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fish-gameI 

"CONSERVATION OF WILDUFE THROUGH EDUCATION" 



California Fish and Game is a journal devoted to the conservation of wild- 
life. If its contents are reproduced elsewhere, the authors and the California 
Department of Fish and Game would appreciate being acknowledged. 

Subscriptions may be obtained at the rate of $5 per year by placing an 
order with the California Department of Fish and Game, 1416 Ninth Street, 
Sacramento, California 95814. Money orders and checks should be made out 
to California Department of Fish and Game. Inquiries regarding paid sub- 
scriptions should be directed to the Editor. 



Complimentary subscriptions are granted, on a limited basis, to libraries, 
scientific and educational institutions, conservation agencies, and on exchange. 
Complimentary subscriptions must be renewed annually by returning the post- 
card enclosed with each October issue. 



Please direct correspondence to: 

Kenneth A, Hashagen, Jr., Editor 
California Fish and Game 
1416 Ninth Street 
Sacramento, California 95814 



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VOLUME 65 



JULY 1979 



NUMBER 3 




Published Quarterly by 

STATE OF CALIFORNIA 

THE RESOURCES AGENCY 

DEPARTMENT OF FISH AND GAME 

—LDA— 



STATE OF CALIFORNIA 
EDMUND G. BROWN JR., Governor 



THE RESOURCES AGENCY 
HUEY D. JOHNSON, Secretary for Resources 



FISH AND GAME COMMISSION 

SHERMAN CHICKERING, President 
San Francisco 

ELIZABETH L. VENRICK, Vice President ABEL GALLETTI, Member 

Cardiff Los Angeles 

BERGER 0. BENSON, Member RAYMOND DASMANN, Member 
San Mateo Nevada City 



DEPARTMENT OF FISH AND GAME 

E. C. FULLERTON, Director 

1416 9th Street 

Sacramento 95814 



CALIFORNIA FISH AND GAME 
Editorial Staff 

KENNETH A. HASHAGEN, JR., Editor-in-Chief Sacramento 

DARLENE A. OSBORNE, Editor for Inland Fisheries Sacramento 

RONALD M. JUREK, Editor for Wildlife Sacramento 

J. R. RAYMOND ALLY. Editor for Marine Resources Long Beach 

DAVID A. HOOPAUGH, Editor for Salmon and Steelhead Sacramento 

DONALD E. STEVENS, Editor for Striped Bass, Sturgeon, and Shad Stockton 

KIM McCLENEGHAN, Editor for Environmental Services Rancho Cordova 



CONTENTS 



139 



Page 



Effects of a 305-mm (12.0-Inch) Minimum Size Limit on 
Largemouth Bass, Micropterus salmoides, at Merle Collins 
Reservoir Ronald J. Pelzman 141 

The Standing Stock and Production of Eelgrass, Zostera 
marina, in Humboldt Bay, California 
Lawrence W. Harding and James H. Butler 151 

Estimating Fetus Age and Breeding and Fawning Periods in the 

North Kings River Deer Herd Hal Salwasser and Stephen A. Holl 159 

Notes 

Hematological Stress Response of Rainbow Trout, Salmo 
gairdneri, to a Simulated Geothermal Steam Condensate 
Spill James A. Steele and Louis A. Courtois 166 

Observations of Fingerling Chinook Salmon in the Stomachs 
of Yellow Perch from the Klamath River, California 
Trygve F. Dahle, III 168 

An Abnormally Pigmented Shortspine Thornyhead, Sebas- 

to/obus a/ascanus Qean William H. Barss 168 

A Juvenile Ocean Triggerfish, Canthidermis maculatus 
(Bloch), (Pisces, Balistidae) from the Gulf of California 
Robert A. Behrstock 169 

A Pacu ( Colossoma, Family Characidae) Caught in the Sacra- 
mento River Martin R. Briltan and Gary D. Grossman 170 

Effect of First Pectoral Fin Ray Removal on Survival 
and Estimated Harvest Rate of White Sturgeon in the 
Sacramento-San Joaquin Estuary David W. Kohlhorst 173 

Evidence of Successful Reproduction of Steelhead Rainbow 
Trout, Salmo gairdneri gairdneri, in the Ventura River, 
California William E. Tippets 177 

Notes on a Hybridization Experiment Between Rainbow and 

Golden Trout J. R. Gold, R. E. Pipkin, and G. A. E. Gall 179 

California Condor Survey, 1978 

Sanford R. Wilbur, Robert D. Mallette, and John C. Borneman 183 

The Relationship Between Megalopae of the Dungeness Crab, 
Cancer magister, and the Hydroid, Velella velella, and 
Its Influence on Abundance Estimates of C. magister 
Megalopae Daniel E. Wickham 184 

Winter Food Habits of Fishers, Martes pennanti, in Northwest- 
ern California William E. Grenfell and Maurice Fasenfest 186 

An Anti-roll Beach Seine Range D. Bayer 189 

Term Fetuses From A Large Common Thresher Shark, Aloplas 

vulplnus Mark A. Hixon 191 



140 CALIFORNIA FISH AND CAME 



IN MEMORIAM 

John E. Skinner 

We have lost a close friend and a dedicated, innovative fishery biolo- 
gist. John E. Skinner, 52, died in a tragic home fire in the early morning 
hours of December 19, 1978. His home was in Rancho Cordova, near 
Sacramento, where he lived with his wife Marjory and four of their six 
children. Although hurt, the remainder of the family survived. 

John was employed by the California Department of Fish and Game 
for nearly 25 years. He was Coordinator of the State Water Use Planning 
Project since March 1976, working closely with the California Water 
Commission and the Department of Water Resources. 

A native of Detroit, Michigan, he was a graduate of Michigan State 
University with a degree in fisheries and wildlife. He served as a machin- 
ist's mate in the U.S. Navy at the close of World War II and worked as 
a journeyman carpenter and in aircraft fabrication and metallurgy. 

John joined the California Department of Fish and Game early in 1954 
as a Junior Aquatic Biologist assigned to the Inland Fisheries Branch. His 
assignments over the years included 3 years as a researcher on statewide 
angling statistics and on the fisheries of the Sacramento-San Joaquin 
Delta, more than 9 years as Water Projects Supervisor, and 8 years as 
Research Supervisor on the Bay-Delta Study. Among John's technical 
publications is the classic 225 page document, "An Historical Review of 
the Fish and Wildlife Resources of the San Francisco Bay Area". 

He was the current president of the Western Division of the American 
Fisheries Society and was a former president, vice-president, and secre- 
tary-treasurer of the California-Nevada Chapter. He was also affiliated 
with the Pacific Fishery Biologists and the Western Section of the Wildlife 
Society, of which he was a one-time member of the Executive Board. The 
various professional committees he worked on are too numerous to 
mention. 

John was also very active in civic, school, and church affairs. He was 
a member of the California Commonwealth Club and the philosophy and 
goals committee of Folsom-Cordova Unified School District. He served 
as president of the St. John Vianney parochial school board and was past 
president of the school's Parents Club. 

The foregoing summarizes his impressive accomplishments and con- 
tributions, yet does not describe John as a person. What set John apart 
from others was the monumental enthusiasm and dedication with which 
he met any challenge, whether it was cooking a cioppino dinner for 400 
people at the Western Division meeting or solving some major resource 
protection problem. Because of his strong faith in people, he often kin- 
dled in them these same attributes. — Almo Cordone 



LARCEMOUTH BASS MINIMUM SIZE LIMITS 141 

Calif. Fish and Came 65 ( 3 ): 1 4 1 - 1 50. 1 979. 

EFFECTS OF A 305-MM (12.0-INCH) MINIMUM SIZE LIMIT 

ON LARCEMOUTH BASS, MICROPTERUS SALMOIDES, 

AT MERLE COLLINS RESERVOIR ^ 

RONALD J. PELZMAN 

California Department of Fish and Came 

Inland Fisheries Branch 

987 Jedsmith Drive 
Sacramento, CA 95819 

A 305-mm minimum size limit on largemouth bass, Micropterus sdlmoides, im- 
posed in 1972 at Merle Collins Reservoir, Yuba County, was evaluated by in exten- 
sive creel census. Angler harvest of largemouth bass was reduced over 50%, with 
good public acceptance and without reductions in game fish yields. Combined 
annual weights of largemouth and smallmouth bass, M. dolomieui, decreased only 
about 3%. The size limit apparently also protected smallmouth and spotted bass, M. 
punctulatus, less than 305 mm total length. 

INTRODUCTION 

Size limits have been used by other states to control overharvest of 
largemouth bass and to attain desirable predator-prey structure by protecting 
bass large enough to prey on slow-growing panfish and other fishes which 
compete with smaller bass (Funk 1974). Estimated annual exploitation rates as 
high as 0.65 at Merle Collins Reservoir ( Rawstron and Hashagen 1 972 ) prompt- 
ed the Fish and Game Commission, at the request of the Department, to impose 
an experimental 305-mm size limit on largemouth bass in March 1972. 

A continuing creel census begun in 1965 provided a means to follow the 
effects of the size limit on the fishery and to assess its value as a management 
tool. Hashagen (1973) provides detailed information on the census through 
1972 and a description of Merle Collins Reservoir and its fishery. 

METHODS AND MATERIALS 

A creel census, modified from Best and Boles (1956), was the principal 
method used to evaluate the size limit. From June 1965 through June 1977, 
departing anglers were censused at the only point of exit from the reservoir on 
two rotating weekdays per week, on all weekend days, and on all national 
holidays. All anglers were interviewed each census day from 9:00 a.m. to dusk 
and a substantial proportion of all fish were weighed and measured. 

During the spring, summer, and fall of 1973 and 1974, a complete census was 
conducted for seven continuous days and nights to determine how many anglers 
were missed by the 9:00 a.m. to dusk census. The complete census showed that 
about 30% of the anglers were not censused on regular census days. Missed 
anglers included those who stayed in the campground for two or more days 
before passing the census station, and anglers who fished only during the early 
morning hours or at night. 

Creel census data were expanded to give estimates of total catch by mutiply- 

' This work was performed as part of DIngell-johnson Project F-18-R, "Coldwater Reservoir and Special Experi- 
mental Reservoir Management Program", supported by Federal Aid to Fish Restoration funds. Accepted for 
publication January 1979. 



142 CALIFORNIA FISH AND CAME 

ing the observed monthly weekday catch of each species by the ratio of the total 
number of weekdays in a month to the total weekdays censused and adding the 
observed catches for weekends and holidays. Monthly estimates were then 
summed to obtain annual estimates. These were further expanded in all years 
by 30% (as determined by complete creel checks) to account for anglers not 
censused. Estimated total pounds of fish caught annually were calculated by 
multiplying the estimated total monthly catch of a species by the average month- 
ly weight for that species and summing monthly estimates. Total annual pound- 
ages were included in the tables in addition to yield values since mean annual 
surface acreage, which typically fluctuates, was used to calculate yield. 

An interview was included as part of the census in May 1973 to gain informa- 
tion on the number of bass caught and released. Anglers were questioned 
regarding fish preference, whether they were fishing for bass, v. hether they 
released any bass, and sizes of released bass. 

Data from 1 968 through 1 971 and 1 973 through 1 976 were chosen to evaluate 
the size limit since they appeared most representative. Annual weights for 
largemouth bass for 1968 through 1970 were nearly identical (Hashagen 1973), 
indicating a stabilization of the fishery. Data for years 1965 through 1967 were 
excluded because the bass fishery was dominated by an extremely large 1964 
year class which grew slowly and suppressed bass recruitment. Data for 1977 
were not included because drought conditions severely reduced angler effort. 
Data for 1965 through 1967 are included for reference only. 

Catch and effort values typically fluctuate from year to year. For this reason, 
pre- and post-size limit data were compared by averaging values for the two 
4-year periods. 

RESULTS 
General 

Angler use pre- and post-imposition of the size limit was comparable. Over 
the period 1 968 through 1 971 , the number of anglers annually using the reservoir 
averaged 17,316 and the number of hours they expended averaged 76,242. 
Respective values for the period 1973 through 1976 were 19,256 and 82,482 
(Table 1 ). The average number of hours annually expended by "bass anglers", 
defined by Hashagen (1973) as boat anglers fishing during March, April, May, 
and June using lures, minnows, or a combination of these methods, increased 
from 9,571 before 1972 to 14,769 after 1972 (Table 2). 

Annual weight landed and yield values for all game fishes combined and for 
all centrarchids combined before and after the size limit were comparable. 
Pre-size limit annual weight for all game fishes averaged 4,823 kg with a corre- 
sponding yield value of 13.5 kg/ha. Respective post-size limit values were 4,664 
kg and 13.6 kg/ha (Table 1 ). Pre-size limit annual weight for all centrarchids 
combined averaged 2,453 kg with a yield value of 6.8 kg/ha. Post-size limit 
values were 2,500 kg and 7.4 kg/ha. Combined annual weights of largemouth 
and smallmouth bass decreased only about 3%, from a pre-size limit yearly 
average of 1,786 kg to a post-size limit average of 1,731 kg (Tables 2 and 3). 

Largemouth Bass 
Pre- and post-size limit data show that after 1972 anglers caught nearly as 
many largemouth bass as before but retained about 52% fewer. From 1968 



LARGEMOUTH BASS MINIMUM SIZE LIMITS 



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LARCEMOUTH BASS MINIMUM SIZE LIMITS 145 

through 1971, anglers kept a total of 14,649 fish compared to 6,957 retained from 
1973 through 1976 (Table 2). The mean total weight of largemouth bass caught 
and retained annually declined from 1,454 kg for pre-size limit years to 1,109 kg 
for post-size limit years, about a 24% decrease. There was a corresponding 22% 
decline in mean yield of from 4.1 kg/ha to 3.2 kg/ha. As could be expected, the 
mean length and mean weight of creeled fish increased. 

There apparently was no reduction in the catch per hour (bass kept and bass 
released in combination) for "bass anglers". The catch per hour for largemouth 
bass retained by this group decreased over 60%, however (Table 2). 

The size limit was favorably accepted by the majority of anglers. Only 431 
sublegal largemouth bass were observed by the census clerks from 1973 through 
1976. During this period, anglers creeled an estimated 6,957 legal fish and 
reported releasing 10,210 sublegal and 1,953 legal fish (Table 2). It is not known 
how many of the released fish were caught more than once. Also, it is not known 
how many of the released largemouth were actually smallmouth bass reported 
by anglers who could not differentiate between the two species. 

Smallmouth and Spotted Bass 
Anglers caught considerably more smallmouth bass after imposition of the size 
limit. The mean annual catch from 1968 through 1971 was 928 compared to 
1,352 for the 4 years after 1972, an increase of about 46% (Table 3). This does 
not reflect the 3,294 smallmouth bass that anglers reported releasing from 1973 
through 1976. The mean annual weight of smallmouth retained increased about 
88% and yield values doubled after 1972. Mean length and mean weight in- 
creased substantially, the latter by 50%. Spotted bass, introduced in 1970, were 
not observed in the catch until 1973. Mean total length was greater than 305 mm 
in most post-size limit years (Table 4). 

TABLE 4. Spotted Bass Catch Statistics 

1970 1971 1972 

Estimated annual catch tor all anglers _ _ _ 

Estimated annual weight (kg) _ _ _ 

Mean fork length (mm) _ _ _ 

Mean weight (g) _ _ - 

Yield value (kg/ha) 

Other Centrarchids 
The annual catch of redear sunfish Lepomis microlophus, more than doubled 
after 1972 (Table 5). Following the size limit, the annual weight increased by 
nearly 98%, while yield values doubled. There was, however, little change in the 
mean length or mean weight of fish observed in the census. Yield, annual catch, 
and annual weight landed for bluegill, L. macrochirus, declined by about 20% 
following 1972 (Table 6). Mean weight increased by about 53%, while mean 
length increased slightly. Annual catch, annual weight, and yield values for black 
crappie, Pomoxis nigromaculatus, decreased following 1972 (Table 7). Mean 
length and mean weight increased, however, the latter by about 69%. Mean 
length and mean weight of green sunfish, L. cyanellus, increased after 1972 
(Table 8). Declines occurred, however, in all other catch figures. 



YEAR 








1973 


1974 


1975 


1976 


22 


13 


32 


28 


1 


2 


7 


5 


270.4 


343.8 


336.5 


320.2 


244.9 


635,0 


621.4 


412.8 


0.00 


0.01 


0.02 


0.02 



146 



CALIFORNIA FISH AND CAME 






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148 CALIFORNIA FISH AND CAME 

DISCUSSION 
Imposition of a size limit on largemouth bass carries with it the potential for 
certain negative impacts: 

( 1 ) A decline in the growth rate of largemouth bass resulting in the stockpiling 
of fish at lengths below the size limit. 

(2) Overpredation on species which provide angling opportunity as well as 
forage. 

(3) High mortality of angler caught undersized bass which are released. 

(4) Low angler acceptance with a subsequent decline in fishing effort. 
Creel census data and observations made during electrofishing operations 

provided no evidence that any of these occurred following establishment of the 
size limit at Merle Collins Reservoir. 

Following reductions in the take of largemouth bass, other states have report- 
ed the stockpiling of bass at lengths just under a size limit (Funk 1974). Appar- 
ently this did not occur. Electrofishing operations conducted from 1973 through 
1 977, years of average to below average reproduction ( R. Rawstron, Assoc. Fish 
Biol., Dept. Fish and Game, pers. commun.) did not show unusually large 
numbers of bass from 203 mm (the size most bass entered the catch in the 
absence of a size limit) to 304 mm total length (tl). It is reasonable to assume 
that in 1972, the year the size limit was instituted, a group of fish in this range 
was largely protected from angling mortality. Most of these fish, however, likely 
entered the catch during the following year and were replaced in the protected 
group by fish produced in 1971. This probably occurred each year. Stockpiling 
of bass just under the size limit would likely occur when growth rates are 
seriously retarded (Funk 1974). Preliminary analysis of age and growth data 
based on scale measurements indicates that a decline in the growth rate of 
largemouth bass at Merle Collins Reservoir did not occur during the period of 
this study. 

Results of this study do not indicate that protected largemouth bass effected 
a substantial reduction in the panfish forage base. Considerable numbers of 
panfish less than 102 mm tl, particularly bluegill, were observed during electro- 
fishing work in years following 1972. 

Because hooking mortality will diminish the effectiveness of size restrictions, 
it was essential that the magnitude of immediate and delayed mortality of 
sublegal fish be determined. Therefore, a companion study was conducted from 
January through March 1976 at the Department's Field Station in Sacramento to 
assess hooking mortality of sublegal largemouth bass. Results of this study sug- 
gest that direct mortality due to hooking is not a factor which materially reduces 
the value of size limit regulations (Pelzman 1978). 

Angler acceptance of the size limit was good. Most anglers interviewed ex- 
pressed satisfaction with the regulation and some traveled considerable dis- 
tances to fish at the reservoir because of the size limit. Anglers organized into 
clubs were especially supportive. 

Tagging studies of largemouth bass conducted before and after the size limit 
provided comparable estimates of annual exploitation and survival rates. Raw- 
stron and FHashagen (1972) reported an exploitation rate of 0.65 and survival 
rates of 0.24 and 0.19 in 1968 and 1969, respectively, for fish > 203 mm (8.0 
inches) fork length (FL). Exploitation and survival rates of 0.60 and 0.21, respec- 



LARCEMOUTH BASS MINIMUM SIZE LIMITS 149 

lively, for fish >305 mm tl were recorded in 1973 (Rawstron and Pelzman 
1978). 

Substantial increases in the annual catch of smallmouth bass were recorded 
following establishment of the size limit. While the size limit may have contribut- 
ed to increases in the smallmouth take, the increasing smallmouth population 
played a substantial role. The estimated annual take of smallmouth steadily 
increased to a high of 1,500 fish in 1971, the year before the size limit was 
imposed. During the 4 years following 1972, the annual catch averaged 1,352 
fish, compared to 928 for the 4 years prior. A tagging study of smallmouth bass 
> 203 mm FL, initiated in 1976, provided a weighted estimate of mean annual 
exploitation rate of 0.66 and an estimated survival rate of 0.1 6 ( Pelzman, Rapp, 
and Rawstron, in prep.). These values are comparable to those for largemouth 
bass at Merle Collins Reservoir (Rawstron and Hashagen 1972; Rawstron and 
Pelzman 1978). 

The size limit apparently protected smallmouth bass less than 305 mm tl in 
that they were released by anglers unable to distinguish them from largemouth. 
Angler interviews revealed that species identification was a common problem 
among anglers. An increase of over 25.4 mm in the mean length of smallmouth 
in the catch following imposition of the size limit suggests that anglers selected 
for fish that met the largemouth size requirement. In no year after the size limit 
was in effect was the mean total length for smallmouth bass less than 305 mm 
(Table 3). 

Spotted bass constituted only a minor portion of the Merle Collins Reservoir 
fishery. It is probable, however, that the size limit served to protect spotted bass 
since very few anglers could differentiate them from largemouth bass. Twenty- 
three of the 38 spotted bass measured in the census from 1973 through 1976 
were 305 mm or greater tl. Considerable increases in the spotted bass popula- 
tion were noted during electrofishing operations in 1975, 1976, and 1977. Most 
fish observed were less than 305 mm in length. 

The annual catch of redear sunfish more than doubled (118%) after 1972, 
while bluegill catches decreased by about 20%. These changes are more likely 
related to population shifts that began before 1972 than to an influence of the 
size limit. Pre-size limit census data showed that redear were steadily increasing 
in the catch. Observations made during electrofishing operations conducted 
prior to 1972 suggested that redear were replacing bluegill as the dominant 
panfish. Large numbers of bluegill less than 102 mm tl, however, were observed 
during electrofishing work in 1976 and 1977. It is not known if changes in catch 
data for black crappie or green sunfish were related to the size limit. 

Several events occurred at Merle Collins Reservoir following 1972 which 
altered the fishery and may have affected the impact of the size limit: 

(1 ) Threadfin shad, Dorosoma petenense, which had been present in large 
numbers and provided an important food item for bass since 1967, unex- 
pectedly declined in numbers beginning in 1974; only a few were ob- 
served during electrofishing operations in 1 975 ( 6 fish ) and 1 976 ( 3 fish ) . 

(2) The number of catchable trout planted at the reservoir annually was 
increased considerably. 

(3) A severe drought, which affected much of California, reduced water 
levels in late 1975 and in 1976. 

2—78.025 



150 CALIFORNIA FISH AND GAME 

(4) Largemouth bass reproduction was below average during most years 
following 1972; a phenomenon which may have been related to water 
level manipulations. 

It is difficult to relate certain changes in the fishery of Merle Collins Reservoir 
after 1972 to the size limit because of the complexity of the reservoir environ- 
ment and because of the abnormal events listed above. Similarly, detection of 
changes in predator-prey structure is difficult. Census data and observations 
made during electrofishing operations do not suggest that intermediate-sized 
panfish were substantially reduced in number. This study has shown, however, 
that the size limit reduced angler harvest of largemouth bass, a desired result of 
minimum size limits (Funk 1974). This was accomplished with good public 
acceptance and without reductions in angler effort or total yield of game fish. 
Evidence was gathered to indicate that the size limit also protected smallmouth 
and spotted bass less than 305 mm long. As these findings became apparent, size 
limits were applied to all black bass at Merle Collins Reservoir and 26 other 
California waters. 

ACKNOWLEDGMENTS 
Robert R. Rawstron initiated and administered the creel census at Merle 
Collins Reservoir until 1975. Many seasonal aids, too numerous to list, ably 
served as census clerks during the study period. Charles E. von Geldern, Jr. made 
helpful editorial suggestions. 

REFERENCES 

Best, E. A , and H D Boles. 1956. An evaluation of creel census methods. Calif. Fish Came, 42(2): 109-115. 

Funk, J. L., ed. 1974. Largemouth bass harvest in the midwest, an overview. Symposium on overharvest and 
management of largemouth bass in small impoundments. North Cent. Div., Amer. Fish. Soc, Spec. Pub. No. 
3, )ulv 1974. 116 pp. 

Hashagen, K. A., Jr. 1973 Population structure changes and yields of fishes during the initial eight years of 
impoundment of a warmwater reservoir. Calif Fish Came, 59(4): 221-244. 

Pelzman, R. ]. 1978. Hooking mortality of juvenile largemouth bass (Micropterus salmoides). Calif Fish Came, 
64(3): 49-52. 

Rawstron, R. R., and K. A. Hashagen, )r. 1972. Mortality and survival rates of tagged largemouth bass (Microp- 
terus salmoides) at Merle Collins Reservoir. Calif. Fish Came, 58(3): 221-230 

Rawstron, R. R., and R. J. Pelzman. 1978. Comparison of floy internal anchor and disk-dangler tags on 
largemouth bass (Micropterus salmoides) at Merle Collins Reservoir Calif Fish Game, Mil): 121-123. 



HUMBOLDT BAY EELCRASS STOCKS 151 

Calif. Fish and Came hS(l). 151-158. 1979. 

THE STANDING STOCK AND PRODUCTION OF 
EELCRASS, ZOSTER A MARINA, IN 
HUMBOLDT BAY, CALIFORNIA ^ 

LAWRENCE W. HARDING, JR.^ 

Hopkins Marine Station of 

Stanford LJniversity 

Pacific Grove, California 93950 

and 

JAMES H. BUTLER 

Department of Oceanography 

Humboldt State University 

Areata, California 95521 

Measurements of the eelgrass, Zostera marina, standing stock in Humboldt Bay, 
California, were conducted on seven occasions from June 1971 through August 1972. 
The distribution of eelgrass in the Bay was initially determined by mapping the 
Zostera beds in extensive surveys using light aircraft, automobiles, and small boats. 
Following these preliminary studies, eelgrass samples were periodically taken from 
representative sites in the eelgrass beds. These studies were performed in an effort 
to determine the contribution of eelgrass to primary production in Humboldt Bay 
relative to that of the phytoplankton, and to estimate the annual production of 
eelgrass by repeated collection of samples throughout the year. Values ranged from 
1.4 X 10* kg dry wt in April 1972 to 6.9 X lO*- kg dry wt in )uly 1972. South Humboldt 
Bay eelgrass accounted for 78 to 95% of the total stock. The area supporting Z. 
marina growth was 12.2 x lO*" m^. Densities of plant biomass ranged from 0.03 to 
0.73 kg dry wt/m^, with highest values recorded for south Humboldt Bay beds. A 
minimum value for eelgrass production was estimated from the seasonal increase in 
standing stock and published values for carbon content. Production for the April- 
July interval was 1.48 g C/m^/day. Minimum eelgrass production for Humboldt Bay 
was 18.1 X lO*" g C/day. The value for eelgrass production for this interval in Hum- 
boldt Bay was similar to that reported for phytoplankton production measured over 
the same period. This level of primary production is comparable in magnitude on an 
areal basis to those of highly productive cultivated systems and rich coastal and 
estuarine regions. 

INTRODUCTION 

Eelgrass, Zostera marina, grows on broad expanses of intertidal mudflats in the 
two major regions of Humboldt Bay, California (Figure 1 ). The biomass density 
and area of coverage are so large as to render the Zostera beds one of the most 
prominent features of the Humboldt Bay estuary. This study is an examination 
of the eelgrass standing stock and production in Humboldt Bay. Our preliminary 
studies indicated that changes had occurred both in the density of biomass and 
the distribution of eelgrass during the 10-year interval since earlier studies were 
completed (Keller 1963; Keller and Harris 1966). The importance of Z marina 
to primary production in the Bay prompted further quantitative investigation for 
comparison with previous studies and for evaluation of the status of the Hum- 
boldt Bay eelgrass population. 

Zostera marina is an important primary producer in the temperate waters of 
northern hemisphere estuaries and sheltered embayments. This seagrass com- 

' Performed under the auspices of the United States Energy Research and Developme-^' Administration. Accepted 

for publication February 1979. 
^ Current address: University of California, Santa Barbara, DeparJnent of Biological Sciences, Santa Barbara 

California 93106. 



152 



CALIFORNIA FISH AND CAME 



ARCATA 




w9; 



PACIFIC OCEAN 



^. 



NORTH BAY 



EUREKA 



CENTRAL 
BAY 




SCALE 
1 



MILES 
 I 
3 4 



SOUTH 
BAY 



Figure 1. Eelgrass beds and sampling locations in Humboldt Bay, California. 

prises the base of a complex food web and provides habitat for a diverse 
assemblage of associated organisms. Various aspects of eelgrass biology have 
been discussed before (Peterson and Boysen-Jensen 1911; MacGinitie 1935; 
Cottam and Munro 1954; Thayer, Wolfe, and Williams 1975). For a complete 
literature survey on Z marina, consult Phillips (1964) and McRoy and Phillips 
(1968). 



HUMBOLDT BAY EELCRASS STOCKS 153 

Before 1931, very little attention was given to the populations of this aquatic 
angiosperm. A sudden decline in eelgrass standing stocks, and the subsequent 
reduction in commercial fish yields along the eastern seaboard of North Ameri- 
ca, prompted numerous investigations of community interrelations of Zostera 
(Cottam 1934; Stauffer 1937; Moffitt and Cottam 1941; Dexter 1944, 1953). 
Peterson (1918) recognized early the economic importance of Z marina as he 
traced the diet of cod and other commercially important species and suggested 
that eelgrass formed the autotrophic base of those food chains. Later studies 
associated with the eelgrass blight emphasized the importance of Zostera to the 
production of mollusks, crustaceans, annelids, and other animal forms. Recent 
investigations have confirmed the importance of eelgrass as both substratum and 
habitat for a diverse estuarine flora and fauna (Marsh 1973; Rasmussen 1973). 

Aside from its direct participation in marine and estuarine food webs, eelgrass 
assumes an important role in the cycling of nutrients. Organic materials from 
natural decomposition processes or sewage effluent are filtered and collected by 
eelgrass leaves and turions (Milne and Milne 1951), providing an additional 
nutrient source for the Zostera community. Nutrients that otherwise would be 
accumulated in sediments or flushed out to sea may thereby be retained by 
eelgrass and recycled within the estuarine system. The functional significance of 
eelgrass in nutrient cycling and biogeochemistry has been discussed further by 
McRoy and Barsdate (1970) and McRoy and Goering (1974). 

Measurements of eelgrass standing stocks have been conducted throughout 
the northern hemisphere (McRoy 1970); several of these studies involved eel- 
grass populations from the west coast of North America. Keller (1963) and 
Keller and Harris (1966) estimated the distribution and biomass of Z marina '\n 
Humboldt Bay. Waddell (1964) studied the effects of oyster dredging on eel- 
grass standing stocks in Humboldt Bay. McRoy (1966, 1968, 1970) examined the 
distribution of eelgrass along the coast of Alaska and performed biomass meas- 
urements at 10 locations. 

Our general approaches in this study involved collecting a temporal series of 
samples from representative sites in the Humboldt Bay eelgrass beds and deter- 
mining the areal distribution and density of biomass of eelgrass in the entire Bay. 
From these data, gathered throughout the year, we hoped to infer the seasonal 
pattern of growth and decline of the Humboldt Bay eelgrass beds, and to 
estimate the proportion of primary production attributable to eelgrass in relation 
to that of the phytoplankton in this estuary. 

MATERIALS AND METHODS 

Estimation of the total biomass of eelgrass in Humboldt Bay required a twofold 
approach: (1 ) determination of the total acreage that supports eelgrass growth 
in Humboldt Bay, and ( 2 ) measurement of eelgrass density at various locations. 
The product of the area and density of biomass values for each eelgrass bed 
yielded the total quantity of eelgrass present. Summing these products provided 
an estimate of the standing stock of Humboldt Bay. 

The total area supporting eelgrass was determined during 1971 and 1972. 
Mapping was conducted on foot and from small boats, automobile, and light 
aircraft. The boundaries of the eelgrass beds were mapped on a U.S. Geological 
Survey Chart (No. 5832) of Humboldt Bay. The areas supporting eelgrass 
growth were determined with a plane planimeter. 



154 ( ALIFORNIA FISH AND CiAME 

Eelgrass beds were subjectively classified according to biomass density as 
supporting light, medium, or heavy growth. The area supporting eelgrass growth 
of each density classification was determined and representative sample sites 
were selected. Five stations in south Humboldt Bay and three in northern Hum- 
boldt Bay were chosen for sampling (Figure 1 ). 

Samples were collected over a 2-day period, with north and south Humboldt 
Bay measurements made on successive days. Similar procedures were em- 
ployed on seven separate occasions from June 1971 through August 1972. Sam- 
pling procedures for the eight representative areas were standardized to 
eliminate bias in the collection of eelgrass. A 1-m ring thrown in a direction 
determined by two successive coin tosses defined the area to be sampled; for 
consistency, the northeast quadrant of the ring was always sampled. Four of the 
samples (each 0.25 m^) were collected from each of the eight sites. All plant 
material within each quadrant was removed, including underground portions, 
which were carefully collected. The samples were stored in plastic bags and 
labeled, returned to the laboratory, and kept in a cold room (6 C) prior to 
processing. 

In the laboratory, eelgrass samples were washed to remove sediment from the 
plant material. Individual samples were subsequently shredded with a knife, 
placed in tared 800-ml beakers, and weighed (for fresh weight). Samples were 
then dried at 60 C to constant weight and dry weights determined. 

RESULTS AND DISCUSSION 

Standing Stock 

The total eelgrass standing stock in Humboldt Bay ranged from 1.4 X 10^ kg 
dry wt in April 1972 to 6.9 X 10^ kg dry wt in July 1972; south Humboldt Bay 
eelgrass beds constituted 78 to 95% of the total dry weight (Table 1). The 
density of plant biomass was consistently higher in south Humboldt Bay than 
in north Humboldt Bay. 

The total eelgrass standing stock for south Humboldt Bay, as determined by 
Keller and Harris (1966), was lower than the value obtained in this study (Table 
2). The difference is partially attributable to the area of coverage considered. 
Keller and Harris (1966) examined only those mudflats above the —1.5 foot 
tidal level. Since a considerable portion of the eelgrass population lies below that 
level, the additional area (about 2.75 X 10*' m^) should have been included in 
their calculations. They also neglected a significant portion of the plant material, 
collecting and drying only the eelgrass turions, thereby underestimating the total 
eelgrass standing stock based on density of biomass measurements. Therefore, 
our higher values do not necessarily indicate increases in the number or size of 
eelgrass beds from 1960 to 1972, but may be the result of more complete 
mapping of subtidal and intertidal areas supporting the growth of Zostera, and 
a more complete sampling of the plant material. 

Results obtained by Keller (1963) on the relative biomass per unit area of 
north and south Humboldt Bay eelgrass were similar to ours. He attributed the 
differences between the regions to sediment composition, tidal flushing, and the 
commercial dredging for oysters in north Humboldt Bay. Most mudflats in north 
Humboldt Bay are lower with respect to tidal height than those in south Hum- 
boldt Bay, but it is doubtful that the relationship between tidal height and 



HUMBOLDT BAY EELCRASS STOCKS 



155 



TABLE 1 



Date 



)une 

Dec 

Apr 

May 

)une 

luly 

Aug 



)une 

Dec 

Apr 

May 

June 

luly 

Aug 



The Densities of Biomass and Standing Stocks of Eelgrass in North and South 
Humboldt Bay, June 1971 Through August 1972 

Density of Density of Percent 

biomass biomass total 

(T±s.e.) (7± s.e.) eelgrass 

No. of (kg fresh I kg dry Total Total in Bay 

samples wt/m') wt/m') (kg fresh wt) (kg dry wt) (dry) 

South Humboldt Bay (area of eelgrass cover = 7.86 x 10* m^) 

1971 12 2.8+1.4 0.2110.11 22.0X10'' 1.65X10* 88.3 

1971 20 2.1 + 1.1 0.32 + 0.09 16.5x10* 2.52x10* 95.1 

1972 19 1.110.3 0.14 10.12 8.6x10* 1.10x10* 78.3 

1972 18 1.9 10.5 0.29 10.06 14.9x10* 2.28x10* 82.6 

1972 20 4.7 12.6 0.61+0.40 36.9x10* 4.79x10* 90.2 

1972 20 6.9 13.9 0.73 10.45 54.2x10* 5.74X10* 83.1 

1972 20 5.4 + 3.9 0.60 10.54 42.4x10* 4.72x10* 82.5 

North Humboldt Bay (area of eelgrass cover = 4.35 x 10* m^) 

1971 12 0.70 10.40 0.05 10.03 3.05x10* 0.218X10* 11.7 

1971 12 0.33 10.20 0.03 10.02 1.44x10* 0.131X10* 4.9 

1972 12 0.45 10.16 0.07 10.04 1.96x10* 0.305x10* 21.7 

1972 12 0.7110.09 0.1110.02 3.09x10* 0.479X10* 17.4 

1972 12 1.0+1.2 0.12 + 0.11 4.35x10* 0.522x10* 9.8 

1972 12 2.5 12.3 0.27 10.22 10.9x10* 1.17x10* 16.9 

1972 12 1.4 11.1 0.23 10.11 6.09x10* 1.00x10* 17.5 



TABLE 2. Eelgrass Standing Stocks and Mean Biomass Densities from Selected Studies 
Conducted Along the Western Coast of North America 

Mean 
biomass 
Total area Total standing stock density 
Location tm^) (kg dry wt) (kg dry wt/m') 

Izembek Lagoon, Alaska 170 X 10* 256 X 10* 1.52 

(McRoy 1970) 
Kinzaroff Lagoon, Alaska 8,71 X 10* 17.0x10* 1.96 

(McRoy 1970) 
Red Head Lagoon, Alaska 0.45x10* 0.1x10* 0.22 

(McRoy 1970) 
Humboldt Bay 12.2 X 10* 1.4-6.9 X 10*° 0.12-0.57° 

(Present study) 
South Humboldt Bay 8.86 X 10* 1.1-5.7 x 10*° 0.14-0.73° 

(Present study) 
South Humboldt Bay 5.55 X 10* 0.9 X 10* 0.16 

(Keller and Harris 1966) 

Range of values for the seven sampling periods in this study 

eelgrass biomass density, as proposed by Keller and Harris (1966), contributed 
much to this difference. The hypothesis does not account for the low eelgrass 
densities at the —1.0 and —1.5 foot tidal levels. Their results did show that the 
eelgrass biomass may be more dense at or below the —1.0 foot level at a 
particular sampling site, but such differences cannot be applied to a comparison 
of two different locations. 



156 CALIFORNIA FISH AND CAME 

Our values (Table 2) indicate that both the eelgrass standing stock and 
biomass density in Humboldt Bay are of similar magnitude to those in the Gulf 
of Alaska lagoons. Previous determinations of standing stock for west coast 
eelgrass (Keller and Harris 1966; McRoy 1970), hov^ever, did not cover a 
sufficient period of time to permit complete assessment of the populations. 
Significant fluctuations in standing stock resulting from seasonal influences ne- 
cessitate the gathering of temporal data. Since samples from the Gulf of Alaska 
lagoons and the earlier south Humboldt Bay study were taken during the sum- 
mer months, standing stock values were probably near the annual maxima for 
the particular study areas. These values can therefore be compared to the higher 
values obtained in this study. 

Eelgrass Production 

A minimum value for eelgrass production during the spring and early summer 
was estimated from the increase in standing stock from April through July 1972. 
Because losses attributable to herbivore grazing and the physical removal of 
broken turions were not considered, the estimate is a minimum value for net 
production; it should not be construed to represent gross production of eelgrass 
in Humboldt Bay. 

The difference in total standing stock between April and July was 5.5 X 10^ 
kg dry wt, representing a mean daily increase of 6.1 X 10'* kg dry wt/day. 
McRoy (1970) used a value of 0.296 g C/g dry wt for estimates of eelgrass 
production in Alaska, a number which corresponds closely to data gathered by 
Udell, Zarudsky, and Dohney (1969) in Hempstead estuary on Long Island. 
With this conversion factor, the change in standing stock and the area of eelgrass 
coverage, a value of 1.48 g C/mVday was calculated for eelgrass production in 
Humboldt Bay. This is less than McRoy's (1970) value of 8 g C/mVday for 
Izembek Lagoon eelgrass in Alaska, but McRoy's measurements were based on 
oxygen evolution, not changes in biomass. 

Our estimate for eelgrass production is similar to the mean phytoplankton 
production rate determined for the same period in Humboldt Bay (Table 3), 
values which are comparable in magnitude to primary production levels in 
highly productive coastal upwelling (Anderson 1964; Ryther 1969) and estuarine 
systems (Williams 1966; Taylor and Hughes 1967) which have been studied. 
These values are also comparable to production figures for Z marina presented 
by Thayer et al. ( 1 975 ) and indicate that eelgrass primary production on an areal 
basis is similar to that of highly productive cultivated crop plants such as corn, 
rice, and hay (Odum 1959). 

TABLE 3. Comparison of Eelgrass and Phytoplankton Production in Humboldt Bay, 
April Through |uly 1972 

Mean daily Mean total 

Area production production 

(m^ X W") (gC/m^/day) (gC X lO^/day) 

Phytoplankton 30.3-65.6 1.05-1.50° 32.3-53.4° 

Eelgrass 12.2 1.48 18.1 

^ Values given are for lower low and higher high water surface areas, respectively (Harding. Cox. and Pequegnat 1978) 



HUMBOLDT BAY EELCRASS STOCKS 157 

The mean daily production of eelgrass in Humboldt Bay was 18.1 X 10^ g 
C/day, and the mean phytoplankton production for Humboldt Bay from April 
to July 1972 was 32.3 X 10^ g C/day for low tide, and 53.4 X 10^ g C/day for 
high tide (Harding, et al. 1978). Because the estimate for eelgrass production 
is a minimum value, the data indicate that total production by eelgrass was of 
comparable magnitude to that of the phytoplankton in Humboldt Bay during the 
spring and early summer of 1972. These data support the conclusion of Williams 
(1973) that production by seagrasses may equal or exceed that of phytoplank- 
ton and contribute substantially to overall production in these rich marine sys- 
tems. 

REFERENCES 

Anderson, C. C. 1 964. The seasonal and geographic distribution of primary productivity off the Washington and 

Oregon coasts. Limnol. Oceanogr. 9: 284-302. 
Cottam, C. 1934. The eelgrass shortage in relation to waterfowl. Am. Came Conf., Trans. 20: 272-279. 
Cottam, C, and D. A. Munro. 1954. Eelgrass status and environmental relations. ). Wild). Manage. 18: 449^60. 
Dexter, R. W. 1944. Ecological significance of the disappearance of eelgrass at Cape Ann, Massachusetts. ). 

Wildl. Manage. 8: 173-176. 

1953. Recession of eelgrass at Cape Ann, Massachusetts. Ecology 34: 229. 

Harding, L. W., Jr., J. L. Cox, and ). E. Pequegnat. 1978. Spring-summer phytoplankton production in Humboldt 

Bay, California. Calif. Fish Came 64: 53-59. 
Keller, M 1963. Growth and distribution of eelgrass (Zostera marina) in Humboldt Bay, California. M.S. Thesis. 

Humboldt State College. Areata, California. 53 pp. 
Keller, M., and S. W. Harris. 1966. The growth of eelgrass in relation to tidal depth. ). Wildl. Manage. 30: 

280-285. 
MacCinitie, C. E. 1935. Ecological aspects of a California marine estuary. Am. Midi. Nat. 16: 629-765. 
McRoy, C. P. 1966. The standing stock and ecology of eelgrass Zostera marina L. in Izembek Lagoon, Alaska. 

M.S. Thesis. University of Washington. Seattle. 138 pp. 

1968. The distribution and biogeography of Zostera marina (eelgrass) in Alaska. Pac. Sci. 22: 507-513. 

1970. Standing stocks and other features of eelgrass (Zostera marina) populations on the coast of 

Alaska. Fish. Res. Bd. Canada, ). 27: 1811-1821. 
McRoy, C. P., and R. ). Barsdate. 1970. Phosphate adsorption in eelgrass. Limnol. Oceanogr. 15: 6-13. 
McRoy, C. P., and |. ). Coering. 1974. Nutrient transfer between seagrass Zostera marina and its epiphytes. 

Nature 248: 173-174. 
McRoy, C. P., and R. C. Phillips. 1968. Supplementary bibliography on eelgrass Zostera marina. U.S. Fish, and 

Wildl. Serv., Spec. Sci. Rep. Wildl. 114. 14 pp 
Marsh, C. A. 1973. Zostera epifaunal community in the York River, Virginia. Chesapeake Sci. 14: 87-91. 
Milne, L. J , and M. ). Milne. 1951. The eelgrass catastrophe. Sci. Am. 184: 52-55. 
Moffitt, )., and C. Cottam. 1941. Eelgrass depletion on the Pacific coast and its effect on the black brant. U.S. 

Dep. Inter. Fish. Wildl. Serv. Leaflet 204. 26 pp. 
Odum, E. P. 1959. Fundamentals of ecology. 2nd ed. W. B. Saunders. Philadelphia 546 pp. 
Peterson, C. C. ). 1918. The sea bottom and its production of sea food. Rep. Dan. Biol. Sta. 25: 1-62. 
Peterson, C. G. )., and P. Boysen-Jensen. 1911. Valuation of the sea. I. Animal life of the sea bottom, its food 

and quantity. Rep. Dan. Biol. Sta. 20: 1-81. 
Phillips, R. C. 1964. Comprehensive bibliography o\ Zostera marina. U.S. Fish. Wildl. Serv. Spec. Sci. Rep Wildl. 

79. 35 pp. 

Rasmussen, E. 1973. Systematics and ecology of the Isefjord marine fauna (Denmark) with a survey of the 

eelgrass (Zostera) vegetation and its communities. Ophelia 11: 1-507. 
Ryther, ). H. 1969. Photosynthesis and fish production in the sea. Science 166: 72-76. 
Stauffer, R. C. 1937. Changes in the invertebrate community of a lagoon after disappearance of the eelgrass. 

Ecology 18: 427-431. 
Taylor, W. R., and ). E. Hughes. 1967. Primary productivity in the Chesapeake Bay during the summer of 1964. 

Chesapeake Bay Inst., Tech. Rep. 34. 31 pp. 
Thayer, G. W., D. A. Wolfe, and R B. Williams. 1975. The impact of man on seagrass systems. Am. Sci. 63: 

288-296. 



158 CALIFORNIA FISH AND CAME 

Udell, H. P., ). Zarudsky, and T. E. Dohney. 1969. Productivity and nutrient values of plants growing in the salt 
marshes of the town of Hempstead, Long Island. Torrey Bot. Club, Bull. 96: 42-51. 

Waddell, ). E. 19M. The effect of oyster culture on eelgrass (Zostera marina) growth. M S Thesis. Humboldt 

Stale College. Areata, California. 48 pp 
Williams, R. B 1966 Annual phytopiankton production in a system of shallow temperate estuaries. Pages 

619-716 in H Barnes, ed. Some contemporary studies in marine science. Hafner Publishing Co., New York. 

1973. Nutrient levels and phyloplankton productivity in the estuary. Pages 59-89 in R. H. Chabreck, 

ed. Proc. Coastal Marsh and Estuary Manag. Symp Baton Rouge Louisiana State Univ. Div. Cont. Educ. 



NORTH KINGS RIVER DEER HERD 159 

Calif. Fish and Came 65 ( 3 ): 1 59-1 65. 1 979. 

ESTIMATING FETUS AGE AND BREEDING AND FAWNING 
PERIODS IN THE NORTH KINGS RIVER DEER HERD ^ 

HAL SALWASSER ^ and STEPHEN A. HOLE ' 

California State University, Fresno 

Fresno, CA 93710 

Hindfoot length was selected as the best parameter for aging late term California 
mule deer, Odocoileus hemionus californicus, fetuses. Regression analysis indicated 
that litter size has a bearing on fetal growth. Therefore, aging models were devel- 
oped for both single and twin fetuses. Estimation of breeding and fawning periods 
based on fetuses aged by the hindfoot length model showed a 3 week peak of 
breeding centered on 1 December, and a 3 week fawning period centered on 22 June. 
The methods described are applicable to any wild deer herd. 

INTRODUCTION 

Knowledge of the breeding and fawning periods of deer herds is important to 
management and research. The purpose of this study was to determine breeding 
and fawning periods of the North Kings River deer herd. In the course of this 
work we needed to develop a method for estimating the age of late term fetuses. 

The North Kings River deer herd is located in Fresno County, California. Other 
recent studies on this herd have dealt with fawn production and survival (Sal- 
wasser, Holl, and Ashcraft 1978) and diets and nutrition during pregnancy ( Holl, 
Salwasser, and Browning 1979). 

Breeding and fawning period estimates are often based on the ages of fetuses 
acquired through special hunts, road kills, and scientific collections (Chattin 
1 948; Robinette and Gashwiler 1 950; Lassen, Ferrel, and Leach 1 952; Taber 1 953; 
Bischoff 1 957 ) . Most fetal aging studies have relied upon morphological changes 
during fetal development. Armstrong's (1950) and Hudson and Browman's 
(1959) keys for whitetailed, Odocoileus virginlanus, and mule deer, O. hem- 
ionus, are the basis for this approach. However, as the fetus enters the last 
trimester of gestation, external changes other than growth are not easily discerni- 
ble. 

Chattin (1948) presented a fetal growth curve based on hindfoot length for 
fetuses up to 170 days old. Hudson and Browman (1959) provided growth 
curves for four physical parameters. These were based on five known-age and 
numerous calculated-age fetuses. Their data terminated at 180 days of fetal age. 
Short (1970) developed linear regression models for mule deer fetuses from 
Hudson and Browman's data. Nellis ( 1 966 ) explored the use of eye lens weights 
for aging mule deer fetuses. He found the technique useful but pointed out that 
lens weight was positively correlated with body weight. Only Short (1970) 
worked with data from fetuses (a sample of three mule deer fetuses) in the last 
month of prenatal growth. Since much of our work was done during this period 
we needed to extend aging curves to full-term. 

An ideal parameter for aging deer fetuses would have the following character- 

' Assistance to this investigation was provided by Federal Aid in Wildlife Restoration Projects W-51-R "Big Came 
Studies" and W-52-R "Wildlife Investigations Laboratory, ' and by the Union Foundation Fund, University of 
California, Berkeley. Accepted for publication January 1979 

^ Current address: Tahoe National Forest, Nevada City, California 95959. 

^ Current address: San Bernardino National Forest, Cajon Ranger District, Star Route Box 100, Fontana, California 
92335. 



160 CALIFORNIA FISH AND GAME 

istics: 1 ) it would change in a predictable and accurately measurable way as the 
fetus gets older, 2) it would be relatively insensitive to environmental variables, 
3) it could be easily and precisely measured by field biologists and researchers 
alike, and 4) it would require a minimum of laboratory and analytical treatment 
to derive the age estimate. 

Unfortunately, as Verme (1963, 1977) has shown, maternal nutrition affects all 
easily measured growth parameters of deer fetuses. Thus, while it is conceivable 
that criteria 1, 3, and 4 could be met, the need for a parameter that is insensitive 
to environmental conditions is not likely to be met exactly. We thus explored 
the use of three parameters that we suspected of being the least influenced by 
maternal nutrition: 1 ) hindfoot length, 2) contour length, and 3) eye lens weight. 
Since the eye lens technique requires extra laboratory work, we felt it would 
have to be far superior to the skeletal growth methods to warrant its use. 

METHODS 

Deer collections were made during the springs of 1971-1975, as described by 
Salwasseret al. (1978). Fetuses from each doe were sexed, tagged for identifica- 
tion, and stored in 10% formalin. They were removed from the preservative in 
the laboratory, rinsed with tap water, and measured. 

Contour length was measured with a cloth metric tape to the nearest millime- 
ter. It is the dorsal length of the fetus from the distal edge of the brown nasal 
patch, along the contour of the head, shoulders and spine to the center point 
on a line drawn across the ischial tuberosities (see Armstrong 1950). In our 
attempts to measure crown-rump and forehead-rump lengths of near-term 
fetuses, we encountered variation due to how the preserved fetus was contorted. 
This problem could have been avoided by measuring fetuses prior to preserva- 
tion. We used the contour length because it is less subject to errors that result 
from deformation of the fetus than are the crown-rump and forehead-rump 
lengths. 

Hindfoot length (HFL) was measured on an "L" shaped device containing a 
metric ruler on the base. The ankle was placed in the angle of the measuring 
board, and the length of the hindfoot, to the nearest millimeter, was read at the 
tip of the hoof. The left hindfoot was measured for standardization. We compen- 
sated for hooves damaged during preservation by estimating the length of hoof 
tips missing. 

Eye lenses were removed and rinsed in tap water. (If the fetus has not been 
in preservative storage, the eyeball should be removed intact and stored in 
fixative prior to removing the lens.) Lenses were oven dried at 80 C until a 
constant weight was achieved. Lenses were removed from the oven, allowed 
to cool for 3-5 minutes, and weighed on a Mettler automatic balance to the 
nearest 0.01 milligram. Weighing was done within 10 minutes of removal from 
the oven. Drying time averaged 12 days. Larger lenses required more time than 
smaller ones. The heavier eye lens was used as the datum for each fetus. 

The estimated average size of fawns at birth was calculated from measure- 
ments of captured fawns and all fetuses that exceeded the smallest captured 
fawn in size. We thus assumed that any fetus equal to or larger than the smallest 
captured fawn was a full-term fetus. 

Fetal parameters were regressed on the number of days since 1 November to 
find the best fit. We had known that all does in the herd bred after this date. 



NORTH KINGS RIVER DEER HERD 161 

October 1 or 1 September should be used in herds that breed earlier. Regressions 
were explored for growth differences according to litter size and fetus sex. The 
influence of doe age is reflected in litter size, as most single fetuses came from 
yearling and 2-year-old does (Salwasser et al. 1978). Abnormally early- or 
late-conceived fetuses were excluded form our development of final growth 
curves. The biological significance of differences in growth equations was judged 
according to the difference in estimated age at a given size. 

RESULTS AND DISCUSSION 

The initial fit of all three parameters to the liner model Y = a + b,, was 
sufficiently good that it was unwarranted to explore transformations or non- 
linear models (HFL against days, r^ = .859). This is consistent with the findings 
of Hudson and Browman (1959), Nellis (1966), and Short (1970) that these are 
linear growth phenomena in mid- to late-term deer fetuses. All three parameters 
are suitable for use as aging criteria. 

However, hindfoot length is the easiest to measure accurately. Since it also 
had the best correlation with number of days since 1 November (r = .94) 
(Figure 1 ), we selected hindfoot length as the best parameter for aging fetuses. 

Six fawns, estimated to be from 1 to 3 days old, were captured in 1975. Their 
average hindfoot length was 237 mm (range 232-246 mm). Their average 
weight was 3,075 g (range 2,800-3,250 g) (Holl 1976). The smallest captured 
fawn was the runt of a set of twins. We inferred from the captured fawn 
data — and from Cowan and Wood (1955); Hudson and Browman (1959); 
Robinette, Baer, Pillmore and Knittle (1973) — that a single fawn, or one of a set 
of twins, must exceed 3,000 g to qualify as a full-term fetus. Nine fetuses met 
this criterion, five singles and two sets of twins. When pooled with the captured 
fawn data, the estimated average size of a full-term fetus was: HFL = 231 mm 
(S.D. = 16, range 192-255 mm), weight = 3,254 g (S.D. = 219, range 2,800- 
3,668 g). 

When the estimated average hindfoot length of a newborn fawn was inserted 
into the regression model for change in hindfoot length of all fetuses since 1 
November, an age of 235 days was predicted. We assumed 204 days to be the 
average gestation period of California mule deer. Dixon (1934) reported 207 
days, Robinette and Cashwiler (1950) reported 202 days, and Short (1970) 
reported 200 days as average gestation periods for the species of Odocoileus. 
Therefore, we adjusted the y-intercept of the model downward by 31 days to 
yield a predicted age of 204 days when hindfoot length reached 231 mm. It was 
further assumed that the regression models for other parameters overestimated 
fetus age by 31 days and adjusted the models for predicting fetal age (Table 1 ). 

TABLE 1. Regression Equations for Predicting Fetus Age from Hindfoot Length, Contour 
Length, or Eye Lens Weight Regardless of Fetus Sex or Litter Size 

n Regression equation r i^ S. E. b^ 

151 Age = 68 -I- .59 (HFL in mm) 960 .921 .014 

151 Age = 45-1- .26 (Contour in mm) 945 .893 .007 

106 Age =76 -I- 1.01 (Lens weight in mg) 945 .893 .035 

S. E. b. is the standard error of the slope coefficient. 

The influence of fetal sex and litter size on hindfoot length was examined with 
the linear regression model (Table 2). Fetal sex apparently had little effect on 
late-term size (Table 3). Males were slightly larger at 100 days, but size differ- 



162 



CALIFORNIA FISH AND CAME 






q> 
o 

CO 






239 



217 



95 



173 



129 



107 



/ 



/ 



A \^. 



/ 



• + + 



/ 



/ 
/ 



/ 



/ 



/ 



/ 
/ 
/ 

 + + . 

/ 
/ + 

/ 
/ 



■+ =F-+ + / 

+ + + A 

/ 

+-H- +.. y 



+ -tt- 



/ ^ 



/ 



+ + 



/ 



r 



¥ 



/ 



/ 



/ 



/ 



10 



51.7 



93 3 



135 



176.7 



218.3 



260 



Figure 



Hindfoot Length (mm) 

Scattergram of fetal hindfoot length versus number of days since November 1 to date 
of collection. The dashed line represents a 45-day span and illustrates the linear relation- 
ship of hindfoot growth with time. 



ences diminished to essentially none at birth. Litter size did make a difference, 
however. Single fetuses were smaller at 100 days, perhaps reflecting the fact that 
most singles came from yearling and 2-year-old does that were breeding for the 
first time. By 200 days, singles exceeded twins by 1 5 mm in hindfoot length. Until 
the causes of these differences become known, we advise the use of different 
aging equations for singles and twins. Since these models were based on fetuses 
with hindfoot lengths ranging from 50 mm to that at full term, the models are 
suitable for aging any fetuses over 100 days old (or fetuses from does collected 
after February in the North Kings herd). Because of environmental variations 
between years and natural variations between does, the late-term ages derived 



NORTH KINGS RIVER DEER HERD 163 

from the aging equations should be interpreted as being accurate to ± 5 days 
at best. 

TABLE 2. Fetus Sex and Litter Size Influences on Hindfoot Growth 

Fetuses n Regression equation r P S. E. b^ 

All 151 Age = 68 -I- .59 (HFL in mm) .960 .921 .014 

Males 78 Age = 65 + .60 (HFL in mm) .960 920 .020 

Females 73 Age = 71 + .57 (HFL in mm) .961 925 .019 

Singles 28 Age = 75 + .53 (HFL in mm) .963 .928 .029 

Twins 114 Age = 65 + .61 (HFL in mm) .963 .928 .016 

' S. E. b. is the standard error of the slope coefficient 

TABLE 3. Relative Growth of Fetuses According to Equations Presented in Table 2 

Hindfoot length (mm) at 

Fetuses Regression equation 100 days 150 days 200 days 

All Age = 68 + .59 (HFL in mm) 54 139 224 

Males Age = 65 + .60 (HFL in mm) 58 142 225 

Females Age = 71 +.57 (HFL m mm) 51 139 226 

Singles Age = 75 + .53 (HFL in mm) 47 142 236 

Twins Age = 65 + ,61 (HFL in mm) 57 139 221 

We believe that the use of a time series analysis of fetal growth with known 
size of newborn fawns is a suitable alternative in developing fetal age curves 
when known-age fetuses are not available. Given a time series collection of 
pregnant does and information on newborn fawn size, a fetal age predictor could 
be developed for any wild deer herd. Special care should be used, however, in 
applying the assumptions about length of gestation period and average size of 
newborn fawns to populations that differ from those reported in the literature. 
Also the time series method described here should not be used in studies in 
which fewer than 20 fetuses are available. 

To determine breeding and fawning periods, the age of a multiple litter was 
assumed to be the age of the largest fetus. The age of each litter was extrapolated 
to determine conception date. Average fawning date was assumed to occur 204 
days after the conception date (Figure 2). 

The earliest breeding occurred on 6 November ( 1 974 ) , the latest on 3 Febru- 
ary (1973), probably during the second or third estrus period. Two-year-old 
does were involved in both cases. In all other years breeding commenced during 
the second week of November and terminated during the third week of Decem- 
ber. The mean dates of breeding ranged from 25 November (1972) to 10 
December (1971). Over the 5-year period, the mean breeding date was 1 
December, and 75% of all breeding occurred within 8 days of that date. 

Fawning on the North Kings range may begin as early as 29 May, but the first 
fawns in most years will be born during the first week in June. The peak 2 weeks 
of fawn drop occur between 14 June and 30 June. Sixty percent of the fawns are 
born during this period. Approximately one-fourth of the fawns are born in early 
July. Yearlings and 2-year-old does bred and fawned about 1 week after prime 
age does. 

The breeding and fawning periods of the North Kings herd are earlier than 
those reported for the Sequoia and Jawbone herds on the Sierra Nevada west 
slope ( Bischoff 1 957 ) . The periods are similar to those of some black-tailed deer, 
O. h. columblanus, herds in California. 



164 



CALIFORNIA FISH AND CAME 



"CD 



o 



c: 

O 



Breeding Dotes 



100 



90 



80 



70 



60 



50 



40 



30 



20 



Now Nov. Nov. Nov. Nov. Dec. 

1-7 8-14 15-2! 22-28 29-5 6-12 

1 



Dec. Dec. 
13-19 20-26 



T 



T 



T 



T 



Cumulative 




Q li l.limi.lTTTTT 



May May June 



June 



June 



June 



23-30 31-6 



7-13 14-20 21-27 28-4 



July July 
5-11 12-19 



Fawning Dates 



Figure 2. Bar histogram of conception and breeding dates of California mule deer in the North 
Kings River herd during 1971-75. 



ACKNOWLEDGMENTS 
We are pleased to acknowledge the assistance and advice of Oscar Brunetti, 
William Longhurst, Guy Connolly, and Karen Shimamoto. John Kie offered valu- 
able comments. Nobu Asami of U.C. Berkeley prepared the manuscript. 



NORTH KINGS RIVER DEER HERD 165 

REFERENCES 

Armstrong, R A. 1950. Fetal development of northern white-tailed deer. Am. Midi. Natur. 43(3): 650-666. 
Bischoff, A. I. 1957. The breeding season of some California deer herds Calif. Fish Came 43(1 ): 91-96. 
Chattin, ) E 1948. Breeding season and productivity in the Interstate deer herd. Calif Fish Came 34(1 ): 25-31. 
Cowan, I. McT., and A. ). Wood. . 1955. The growth rate of the black-tailed deer Odocoileus hemionus colum- 

bianus. ). Wild!. Manage. 19(3): 331-336. 
Dixon, J. S. 1934. A study of the life history and food habits of the mule deer in California: Part I. Life history. 

Calif. Fish Came 20(3): 181-282. 
Holl, S. A. 1976. Fawn production, habitat requirements, and growth in the North Kings deer herd, Fresno 

County, California. MA. Thesis, California State University, Fresno 128 pp. 
Holl, S. A., H. Salwasser, and B. Browning. 1979. Diet composition and energy reserves of California mule deer 

during pregnancy. Calif. Fish Came 65(2): 6&-79. 
Hudson, P., and L. C. Browman. 1959 Embryonic and fetal development of the mule deer. ). Wildl. Manage. 

23(3): 295-304. 
Lassen, R. W., C. M. Ferrel, and H. Leach. 1952. Food habits, productivity and condition of the Doyle mule 

deer herd. Calif. Fish Came 38(2): 211-224. 
Nellis, C. H. 1966. Lens weights of mule deer fetuses. ]. Wildl. Manage. 30(2): 417-419. 
Robinette, W. L., and |. S. Cashwiler. 1950. Breeding season, productivity, and fawning period of the mule deer 

in Utah. ). Wildl. Manage. 14(4): 457^69. 
Robinette, W. L., C. H. Baer, R. E. Pillmore, and C. E. Knittle. 1973. Effects of nutritional change on captive mule 

deer. ). Wildl. Manage 37(3): 312-326. 
Salwasser, H., S. A. Holl, and C. A. Ashcraft. 1978 Fawn production and survival in the North Kings deer herd 

Calif. Fish Came 64 ( 1 ) : 38-52. 
Short, C. 1970. Morphological development and aging of mule and white-tailed deer fetuses. J. Wildl. Manage. 

34(2): 383-388. 
Taber, R. D. 1953. Studies of black-tailed deer reproduction on three chaparral cover types. Calif. Fish Came 

38(2): 177-^43. 
Verme, L. j. 1963. Effect of nutrition on growth of white-tailed deer fawns. Trans. N Am Wildl. Conf 28: 

431^»43. 
1977. Assessment of natal mortality in upper Michigan deer. J. Wildl. Manage. 41(4); 700-708. 



166 CALIFORNIA FISH AND CAME 

NOTES 

HEMATOLOGICAL STRESS RESPONSE OF RAINBOW 
TROUT, Salmo gairdneri, TO A SIMULATED GEOTHERMAL 

STEAM CONDENSATE SPILL 

Steam condensate is a by-product of electrical power production using geo- 
thermal steam at the Geysers, Sonoma County, California. The condensate is 
ordinarily returned to the production zone by reinjection well, but during 1974 
and 1975 eleven major spills occurred in which the condensate reached nearby 
streams. Although fish kills resulted from some of these spills (Department of 
Fish and Game unpublished data), the sublethal effects of the condensate re- 
main undocumented. 

Blood hematology has been used by some researchers to monitor sublethal 
stress response of rainbow trout (Blaxhall 1972, Courtois 1975, McLeay 1975). 
This study was undertaken to determine if hematological characteristics of rain- 
bow trout are affected after exposure to stream condensate under simulated 
stream conditions. 

At condensate concentrations of 5 to 29%, LeGore and Bowen (1976) found 
50% of the rainbow trout died within 96 hours. During low flow (5 cfs) periods 
in streams adjacent to the Geysers, large spills of condensate (e.g., 182,000 liters 
in 4 min on September 5, 1975) could exceed these concentrations. The conden- 
sate would be gradually diluted and carried downstream. Little is known about 
the degree of stress placed upon fish exposed to spills of condensate at low 
concentrations. Monitoring the hematological stress response of rainbow trout 
to the condensate would be valuable in assessing its effect on fish in their natural 
habitat. 

To approximate a condensate spill, 56.8 liters of condensate, collected from 
Geysers Power Plant Unit 6 was added to a 500-liter tank containing 378.5 liters 
of filtered river water and 20 shasta strain rainbow trout from the American River 
Fish Hatchery averaging 1 14 g wet weight and 22 cm fl. This represented a 1 5% 
volume/volume addition to a stream. The added condensate slowly overflowed 
through a standpipe drain which kept the water level constant. An identical tank 
with 20 fish served as an untreated control group. Water in both tanks was 
exchanged at the rate of 60 liters/ hr. Air was bubbled in the tanks through porous 
stones. Carbon dioxide, ammonia, and oxygen levels were monitored in each 
tank using Hach"" prepared reagents. These parameters were altered when 
steam condensate was added to water in preliminary tests. 

Blood from fish in both the control and test tanks was collected immediately 
after beginning the test and at 2 hr, 23 hr, and 93 hr. Individual fish were used 
only once during the test and were not returned to the test tank. Five fish from 
each tank were anesthetized with MS-222 (tricaine menthanesulfonate), and a 
heparinized syringe was used to remove a blood sample via cardiac puncture. 
Hematocrit (PCV) and total hemoglobin (Hb) (cyanmethemoglobin form) 
levels were established using standard techniques (Blaxhall 1972) and serum 
protein values were determined with a hand refractometer (Courtois 1975, 1976; 
Schalm 1975). 

Extreme physiological differences were evident between control fish and test 
fish blood parameters, during these tests. This indicates that even small concen- 



NOTES 167 

trations of geothermal steam condensate will stress rainbow trout. 

Amounts of ammonia (30 mg/l) and carbon dioxide (90 mg/l) were very 
high up to 23 hr after addition of the condensate but had returned to pre-test 
levels by 93 hr. Dissolved oxygen decreased by 1.0 ppm following introduction 
of condensate but returned to the control level for the remainder of the test 
period. These features of condensate may cause the most stress for fish popula- 
tions during a spill. 

The mean corpuscular hemoglobin concentration (MCHC) is a sensitive 
indicator of stress in fish and was determined using hematocrit and hemoglobin 
values MCHC = Hb/PCV (100) (Schalm 1975). MCHC increased sharply 
( -(_1.5 g/lOO ml) following addition of the condensate, dropped below normal 
(_1.3g/100ml) and then remained significantly (95% confidence level) above 
control values (+3.4 g/100 ml) for the duration of the test, indicating an 
increase in mobilization of new blood cells from storage locations. This is a 
typical response to a stressful situation. 

Hatchery-raised fish were used because of their resistance to the stress of 
handling but this increased tolerance may have dampened response results. 
Stress response of rainbow trout over a longer term is not known and would be 
of interest. 

Doudoroff and Katz ( 1 953 ) have shown that sublethal pollution can alter the 
size and structure of wild fish populations. This preliminary study indicates that 
spills of geothermal steam condensate into small streams will influence wild 
populations of rainbow trout. 

ACKNOWLEDGMENT 

We gratefully acknowledge the assistance and space provided by the Water 
Pollution Control Laboratory, California Department of Fish and Game, Rancho 
Cordova, CA, for this experiment. 

REFERENCES 

Blaxhall, P. C. 1972. The hematological assessment of the health of fresh water fish A review of selected 

literature. )our. Fish Bio., 4: 593-604. 
Courtois, L. A. 1975. Hematological assessment and toxicity of antimycin A to golden shiners, Notemigonus 

crysoleucjs. Prog. Fish-Cult., 37(4): 202-204. 
1976. Hematology of juvenile striped bass, Morone saxatllls (Walbaum), acclimated to different envi- 
ronmental conditions. Comp. Biochem. Physiol., 54A: 221-223. 
Doudoroff, P, and M. Katz. 1953. Critical review of literature on the toxicity of industrial wastes and their 

components to fish. Sewage Ind. Wastes, 25: 802-839. 
LeCore, R. S., and W Bowen. 1976. Aquatic toxicity experiments at the Geysers, California. Document No. 

75-074 FR. Parametrix, Inc. Seattle, Wash. 139 p. 
McLeay, D. ]. 1975. Sensitivity of blood cell counts in juvenile coho salmon (Oncorhynchus kisutch) to 

stressors including sublethal concentrations of pulpmill effluent and zinc. Can. Fish. Res. Bd., )., 32(12): 

2357-2364. 
Schalm, O. W. 1975. In Veterinary hematology. Lea and Febigeler, Philadelphia, p 1-12, 66. 

— James A. Steele, Region 3, Yountville, and Louis A. Courtois, Environmental 
Services Branch, Sacramento, California Department of Fish and Game. Mr. 
Steele and Mr Courtois are now with Inland Fisheries Branch, Sacramento. 
U.S. Fish and Wildlife Service Contract 14-16-0001-6048 RBS,"Geothermal 
Resources Assessment Study". Accepted for publication October 1977. 



168 CALIFORNIA FISH AND GAME 

OBSERVATIONS OF FINGERLING CHINOOK SALMON IN 

THE STOMACHS OF YELLOW PERCH FROM THE 

KLAMATH RIVER, CALIFORNIA 

In a study to determine the relationship between yellow perch (Perca flavesc- 
ens) and young salmonids, Coots (1956) examined the stomachs of 731 perch 
collected from March 1951 through March 1952 from the Klamath River in 
California and found no salmonids. Additional perch stomachs were examined 
during a trapping operation for downstream migrant chinook salmon (Oncor- 
hynchus tshawytscha ) fingerlings in February, March, and April 1952, but salmo- 
nids were not noted in their stomachs. 

Under artificial conditions in live traps and aquarium tests with adult perch 
and fingerling salmon. Coots (1956) found that perch would eat the salmon if 
given the opportunity. 

On 7 May 1976, the stomachs of 44 yellow perch taken from the Klamath 
River were examined for the presence of fingerling chinook salmon. These 
samples were collected from the Klamath River in Siskiyou County about 
100 m downstream from the mouth of Bogus Creek just below the Iron Gate Fish 
FHatchery. They were taken in slack water near a brushy bank with a boat- 
mounted electrofisher. 

Fingerling chinook salmon were found in 35 (80%) of the perch stomachs. 
Each of these stomachs contained one to five salmon, 3.2 to 4.4 cm fork length 
(fl). The average length of yellow perch with chinook salmon in their stomachs 
was 15.0 cm fl with a range of 12.2 to 19.8 cm fl. 

At times, yellow perch and fingerling salmon apparently utilize the slack water 
area where the perch were captured, thus providing the opportunity for perch 
to prey on young salmon. If there were extensive areas with the proper condi- 
tions, perch predation on salmon fingerlings could be an important factor in 
salmon survival. 

REFERENCE 

Coots, Millard. 1956. The yellow perch, Perca flavescens (Mitchlll), in the Klamath River. Calif. Fish Came, 
42(3): 219-228. 

— Trygve F. Dahle, III, Inland Fisheries, California Department of Fish and Game, 
627 Cypress Ave., Redding, CA 96001. Present address: 4556 Myrtle Ave, 
Eureka, CA 95521. Accepted for publication April 1978. 

AN ABNORMALLY PIGMENTED SHORTSPINE THORNY- 
HEAD, SEBASTOLOBUS ALASCANUS^^fKH 

On April 17, 1975 a black shortspine thornyhead was caught by the trawler 
Helen Louise •^\\\\q fishing off Coos Bay, Oregon, in about 300 fm. The striking 
color abnormality was brought to my attention by skipper Tom McDonald and 
his crewman. 

The entire fish was darkly pigmented, closely resembling the coloration of a 
sablefish, Anoplopoma fimbria. It was landed with about 2200 kg of normally 
pigmented (red) shortspine thornyheads. It was a female 452 mm total length, 
in excellent condition. This is the only such color abnormality I have observed 
for this species in over 6 years of sampling trawl catches in the Newport- 
Brookings, Oregon area. 

— William H. Barss, Marine Region, Oregon Department of Fish & Wildlife, 
Marine Science Drive, Newport, Oregon 97365. 



NOTES 169 

A JUVENILE OCEAN TRIGGERFISH, CANTHIDERMIS 

MACULATUS (BLOCH), (PISCES, BALISTIDAE) 

FROM THE GULF OF CALIFORNIA 

On 20 August 1972, while dipnetting juvenile fishes at the docks inside San 
Carlos Bay, Sonora, Mexico, I collected an ocean or rough triggerfish, 12.8 mm 
standard length (sl). The fish was swimming under a small raft of seaweed, 
Sargassum sp, in the company of a clinid, Exerpes asper, which is locally abun- 
dant in the Sargassum habitat. The distinctively low meristic counts (D. Ill, 23; 
A. 20; P,. 14) were within the ranges presented by Berry and Baldwin (1966), 
and the general body form agreed with their illustration. However, the pectoral 
fins were more lobed than they showed, the upper rays being four times the 
length of the lower rays. 

Canthidermis maculatus has a circumtropical distribution, being found both 
inshore (rarely) and in surface waters of the open ocean. It is the most wide- 
ranging and probably the most abundant triggerfish in the eastern Pacific, where 
it has been reported from Haucho, Peru, to waters off central Mexico ( Berry and 
Baldwin 1 966) . Of the six triggerfishes reported from the eastern Pacific by Berry 
and Baldwin (1966), three are residents in the Gulf of California: Balistes polyle- 
/9/5Steindachner, Pseudobalistes naufragium (Jordan and Starks), and Sufflamen 
verres (Gilbert and Starks). The addition of Alutera scripta (Osbeck), some- 
times placed in the family Monacanthidae, raised the total to four (Boyd W. 
Walker, pers. commun.). My triggerfish is the fifth balistid recorded from the 
Gulf of California. 

From 28 June to 21 July 1972, I collected about 2,750 juvenile fishes of 
approximately 40 species, in association with floating mats of Sargassum (Behr- 
stock 1975). The collecting was done just outside the mouth of San Carlos Bay, 
about 1 km from the Canthidermis maculatus coWecUon site. My samples includ- 
ed 20 juveniles of the finescale triggerfish, Balistes polylepis, a common species 
in the Gulf of California. Although most of the species I collected probably have 
spawning populations in the vicinity of San Carlos Bay, some, such as Canthider- 
mis maculatus, may have been swept up the east side of the Gulf by the southerly 
winds which predominate during the summer (Roden 1958; Roden and Groves 
1959) and represent expatriates from Pacific Ocean populations. 

ACKNOWLEDGMENTS 

For their comments on the distribution of triggerfishes and/or locality data for 
specimens under their care I would like to thank: Boyd W. Walker and Robert 
R. Harwood, University of California, Los Angeles; Richard FH. Rosenblatt, 
Scripps Institution of Oceanography; Matthew R. Gilligan, University of Arizona; 
and John E. Fitch, California Department of Fish and Game. Permission to collect 
fishes in Mexican waters (Permit No. 4995) was secured through the office of 
the Secretaria de Industria y Comercio, Subsecretaria de Pesca, Direccion Gen- 
eral de Regiones Pesqueras, Mexico City, Mexico. Also, I'd like to thank Gary 
Friedrichsen of Areata, California, for providing transportation and stimulating 
conversation on a most worthwhile field trip. 



170 



CALIFORNIA FISH AND CAME 



REFERENCES 

Behrstock, R. A. 1975. Juvenile development oi Trachinotus kennedyi S\e\ndAchnex (Pisces: Carangidae) from 
the eastern Pacific, with notes on its ecology. Master's Thesis. Humboldt State University. 55 pp. 

Berry, F. H., and W. ). Baldwin. 1966. Triggerfishes (Balistidae) of the eastern Pacific. Calif. Acad. Sci., Proc. 

34(9): 429-474. 
Roden, C. I. 1958. Oceanographic and meteorological aspects of the Gulf of California. Pac. Sci. 12(1 ): 21-45. 

Roden, G. I., and C. W. Groves. 1959. Recent oceanographic investigations in the Gulf of California. ). Mar. 
Resour 18(1): 10-35. 

— Robert A. Behrstock, Department of Fisheries, School of Natural Resources, 
Humboldt State University, Areata, California 95521. Accepted for publication 
May 1978. 



A PACU {COLOSSOMA, FAMILY CHARACIDAE) CAUGHT 

IN THE SACRAMENTO RIVER 

On 10 October 1977, a piranha-like fish was caught by 16-year old Jinnmy 
Seidel of Sacramento, while fishing for catfish using a hook baited with an 
earthworm. The fish was caught on the Yolo County side of the Sacramento 
River near Elkhorn Ferry just above Sacramento. Reports that the fish was an 
illegal piranha led to its seizure by the Department of Fish and Game for identifi- 
cation. The frozen specimen was identified by the senior author as a pacu, a 
largely vegetarian characin of the genus Colossoma. (Figure 1 ) The fish was 
thawed, measurements and counts made, scale samples taken, and the gut 
removed; the stomach and intestine were empty, the lumen of minimum diame- 
ter. 

■p" 






Figure 1. A pacu, Colossoma nigripinnus, 332 mm. total length, caught in the Sacramento River, 
October 10, 1977. Photograph by Martin R. Brittan. 



NOTES 



171 



The fish was a subadult male of 332 mm tl, 294 mm fl, 255 mm SL, having 
lost the spotted and barred juvenile pattern characteristic of Colossoma up to 
about 150 mm SL and attained the adult coloration, in which the back is silver- 
black, the underside of the head and anterior belly pinkish-orange (turning 
silvery after death), and the rest of the body blackish, except for the brownish 
opercle. The silvery-black back and the blackish lower flanks are delineated by 
an irregular "zig-zag" wash (see photo). The greatest body depth is 120 mm 
(47% of SL), head length 88 mm (34% of SL), orbit 15 mm (17% of head 
length), predorsal distance 148 mm (58% of SL), preanal distance 185 mm 
(73% of SL), prepelvic distance 132 mm (52% of SL). There are 90 to 95 scales 
in the lateral line (about 10 on the caudal base); transverse line about 25 scales 
from dorsal to lateral line and 24 from lateral line to midbelly; predorsal scales 
about 47; about 25 midventral serrae to origin of ventrals plus 26 to anus; 8-9 
rows of ventral sheath scales. Dorsal iv,14; anal iv,22; pectoral i,17. Teeth in 
upper jaw in two rows, the 10 in the outer row with an outer incisiform edge, 
the central teeth with dark tips. The six teeth in the inner row have an inner and 
outer incisive edge (not so sharp as that of the outer teeth) with a shallow 
concavity between. ( Figure 2 ) The teeth in the lower jaw total 1 2 in a single row, 
becoming progressively smaller and simpler, the center ones incisorlike, the 
lateral ones becoming conical. (Figure 3) The opercle and subopercle exhibit 
posteriorly-diverging radiating striae. 




Figure 2. Head of pacu, showing upper dentition and fleshy, flap-like lower lip. Photograph by 
Martin R. Brittan. 



172 



CALIFORNIA FISH AND CAME 




Figure 3. Lov/er dentition of pacu. Photograph by Martin R. Brittan. 



The original descriptions of the six nominal species, mostly dating from the 
early and middle 19th century, are sketchy and based on one or only a few 
specimens. There have been no recent revisions of the genus and scientific 
specimens are few, although Colossoma are common food fishes in tropical 
fresh waters of South America. The specimen closely compares to some in the 
California Academy of Sciences identified by Stanley W. Weitzman and William 
I. Follett as Colossoma nigripinnus Cope. Specimens identified as Colossoma 
bidens had much smaller scales. The senior author tentatively identified the 
Sacramento specimen as C. nigripinnus. 

The specimen showed no evidence of disease or parasites. How long it had 
been in the river is not known, but since pacus and piranhas are generally 
sympatric and have comparable ecological requirements, some deductions can 
be made. Temperatures in the Sacramento River were unusually high during 
summer 1977, a drought year, and between mid-May and mid-October were 
above 18 C which is approximately the minimum temperature at which most 
tropical lowland fishes can maintain themselves. Temperatures at which such 
fishes could comfortably exist occurred between mid-)une and mid-September: 
June 28, 25.1 C; July 28, 24.8 C; August 8, 25.0 C; September 13, 23.3 C. The 
higher temperatures are within breeding range. During most years midsummer 
temperatures average about 20-21 C, and in some years run as low as 17-18 C. 
Mid-winter temperatures range from 6.5 to 9.0 C and would be lethal. Evidence 
that the fish did not over-winter comes from the scales, which exhibited no 
growth rings or stress checks. 



NOTES 173 

Gery (1973) and Sterba (1962) give maximum lengths of 60-80 cm and a 
weight of 10 kg for Colossoma. Lovshin, et al. (1974) report seeing the larger 
pacus, called tambaqui, reaching a maximum length of 89 cm and a weight of 
over 13 kg in the Manaus, Brazil, market; they also report that fishermen say 
tambaqui exceed 20 kg. Colossoma grow rapidly in sufficiently roomy aquaria, 
as much as an inch a month. They are frequently a problem when they outgrow 
an aquarium. Our specimen was probably released into the river sometime after 
early June, probably a few days before being caught, in view of the empty 
digestive tract, since there is considerable algae and vegetable debris in the river. 
It is unlikely that this species or others with the same temperature requirements 
( ould overwinter in Northern California waters. However, any new hot water 
discharge into natural waters should be considered to be capable of creating 
survival and/or reproductive conditions. 

REFERENCES 

Gery, ). 1973. Characins and electric eels. In Crzimek, B., Crzinnek's aninnal encyclopedia. Van Nostrand 
Rheinhold Company, New York. 531 p. 

Lovshin, A. B , A B da Silva, |. A Fernandez, and A. Carneiro-Sobrinho. 1974. Preliminary pond culture test 
of pirapatinga (Mylossoma bidens) and tambaqui {Colossoma bidens) from the Amazon River basin. In 
Symposium on aquaculture in Latin America FAO/CARPAS publication 6/74/SE24: 1-9. 

Sterba, G. 1962. Freshwater fishes of the world. Studio Vista, London. 878 p 

— Martin R. Brittan, California State University, Sacramento, CA 95819, and Gary 
D. Grossman, University of California, Davis, CA 95616. Accepted for publica- 
tion January 1978. 

EFFECT OF FIRST PECTORAL FIN RAY REMOVAL ON SUR- 
VIVAL AND ESTIMATED HARVEST RATE OF W^HITE STUR- 
GEON IN THE SACRAMENTO-SAN JOAQUIN ESTUARY 

INTRODUCTION 

Sturgeon ages commonly are estimated from annual growth patterns in cross 
sections of the first, or anterior, ray of the pectoral fin. However, removal of fin 
rays during a tagging study may affect survival of the fish and bias estimates of 
population parameters estimated from tag recoveries. Several authors have 
released sturgeon after removal of the anterior pectoral fin ray without discussing 
the effect on subsequent survival (Cuerrier and Roussow 1951; Pycha 1956; 
Priegel 1973). Bajkov (1949) stated that white sturgeon (Acipenser transmon- 
tanus) appear to withstand removal of a fin ray without any damage, but offered 
no evidence for his conclusions. 

To determine the effect of pectoral fin ray removal on survival and estimated 
harvest rate of white sturgeon, I evaluated tag returns from the Sacramento-San 
Joaquin Estuary, California. 

METHODS 
In fall 1974 sturgeon were captured with trammel nets in San Pablo Bay and 
tagged with disc dangler tags placed beneath the anterior part of the dorsal fin. 
Capture and tagging methods have previously been described (Chadwick 1963; 
Miller 1 972 ) . Five dollar reward tags were used exclusively to assure a high rate 
of angler response. 



174 CALIFORNIA FISH AND CAME 

To determine the age composition of tagged fish, the first ray of the left 
pectoral fin was removed from every second sturgeon tagged. Prior to tagging, 
the fish was placed on its right side on the boat deck and the fin ray was severed 
as close to its articulation as possible. Large cutting pliers or a small hand saw 
were used to cut the ray. This procedure required less than 1 minute per fish. 
To facilitate analysis, fin rays were removed only from fish with odd numbered 
tags. For convenience, I will refer to fish with the fin ray removed as odd 
numbered and those with intact pectoral fins as even numbered. 

Harvest rates were calculated from first year returns of each tag type. Confi- 
dence limits for harvest rates were estimated assuming tag returns followed a 
Poisson distribution. 

I analyzed 3 years of tag returns to determine the effect of pectoral fin ray 
removal. Returns of odd and even numbered tags were compared using a 
standard chi-square test of independence (Sokal and Rohlf 1969). Mortality due 
only to fin ray removal was estimated as: 1 — ratio of odd:even tag return per- 
centages. I estimated survival separately for odd and even numbered tags using 
a linear regression of logarithm of returns against time (Ricker 1975). The an- 
tilogarithm of the slope of the regression line is an estimate of annual survival. 

RESULTS AND DISCUSSION 

A total of 71 2 legal sized (> 1 01 .6 cm total length ) white sturgeon was tagged 
in 1974. Of those, 358 had the first ray of the left pectoral fin removed and 354 
did not. 

The tag returns indicate fin ray removal caused mortality (Table 1 ). During 
the first year, 13 odd numbered and 20 even numbered tags were returned, 
yielding harvest rate estimates of 0.036 and 0.056, respectively. The respective 
95% confidence intervals were 0.019-0.060 and 0.036-0.085. While the differ- 
ence in these return rates was not statistically significant, the difference was 
significant at the end of 2 {X^= 5.24, P < 0.025 ) and 3 ( ^^ = 8.20, P < 0.005 ) 
years due to continued higher returns of even numbered tags. 

The decrease in the ratio of odd:even tag return percentages was relatively 
small after the first year, indicating that most mortality due to fin ray removal 
occurred in the first year. However, the fact that this ratio did decrease suggests 
some mortality occurred during the second year also (Table 1 ). 

After the first year, estimated annual survival of odd numbered sturgeon was 
0.88 and estimated survival of even numbered fish was 0.95 (Figure 1 ). These 
estimates are imprecise since return sample sizes are small and the points do not 
fall in a straight line. 

I conclude that removing the first ray of the pectoral fin of white sturgeon 
causes substantial mortality during the first year and less mortality thereafter. 
Also, consistently greater returns of even number tags in all 3 years indicates that 
mortality from pectoral fin ray removal results in an underestimate of exploita- 
tion and that the best estimate of exploitation rate is based on even numbered 
tags alone. If fin ray removal is used in conjunction with a sturgeon tagging 
program, estimates of population parameters derived from tag recoveries may 
exhibit serious bias. 



NOTES 



175 



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i 


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ithou 


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176 



CALIFORNIA FISH AND CAME 



20r- 



z 
tr 

I- 
UJ 

a: 

CD 

< 

I- 

Q 
LU 

q: 

UJ 



o 

Q 

o 







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r^ = 0.76 

S= antilog,Q(-0.057) = 0.88 



RETURN YEAR 



CO 

z 
a: 

H 
Ijj 

tr 

CD 

< 

I- 

o 

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cr 

LiJ 
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> 

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20 



10 



Log,QY= I.332-0.023X 

r2=0.76 

S= antilog,Q(-0.023)= 0.95 



RETURN YEAR 



FIGURE 1 . Tag returns from white sturgeon tagged in San Pablo Bay in fall 1 974. The antilogarithm 
of slope is an estimate of annual survival rate (S). Slope and survival are calculated 
separately for odd numbered fish with the first ray of the left pectoral fin removed (a) 
and even numbered fish with no fin ray removed (b). 



NOTES 177 

ACKNOWLEDGMENTS 
Richard Fenner and Salvatore Mercuric assisted in the tagging operation and 
Donald Stevens reviewed the manuscript. I thank these individuals for their help. 
This work was perfornned as part of Dingell-Johnson Project California F-9-R, "A 
Study of Sturgeon and Striped Bass", supported by Federal Aid to Fish Restora- 
tion funds. 

REFERENCES 

Bajkov, A. D 1949. A preliminary report on the Columbia River sturgeon. Oregon Fish Comm. Res. Briefs 2(2): 
3-10. 

Chadwick, H. K. 1963. An evaluation of five tag types used in a striped bass mortality rate and migration study. 
Calif. Fish Came 49(2): 64-83. 

Cuerrier, J. -P., and G. Roussow. 1951. Age and growth of lake sturgeon from Lake St. Francis, St. Lavi/rence 
River. Report on material collected in 1947. Can. Fish Cult. 10: 17-29. 

Miller, L. W. 1972. White sturgeon population characteristics in the Sacramento-San loaquin Estuary as meas- 
ured by tagging. Calif. Fish Came 58(2); 94-101. 

Priegel, G. R. 1973. Lake sturgeon management on the Menominee River. Wise. Dept. Nat. Res., Tech. Bull. 
No. 67, 20 pp. 

Pycha, R. L. 1956. Progress report on white sturgeon studies. Calif. Fish Game 42(1): 23-35. 

Ricker, W. E. 1975. Computation and interpretationof biological statistics of fish populations. Fish. Res. Bd. Can. 
Bull. 191, 382 pp. 

Sokdl, R. R., and F | Rohlf. 1969. Biometry. W. H Freeman and Company, San Francisco, 776 pp. 

— David W. Kohlhorst, California Department of Fish and Game, 4001 North 
Wilson Way, Stockton, California 95205. Accepted for publication August 
1978. 

EVIDENCE OF SUCCESSFUL REPRODUCTION OF STEEL- 
HEAD RAINBOW TROUT, SALMO GAIRDNERI CAIRO- 
NERh IN THE VENTURA RIVER, CALIFORNIA 

In recent years there have been scattered reports of adult steelhead trout being 
caught in the Ventura River, Ventura County, fish which could be remrrants of 
a run that once numbered 4-5,000 adults (Clanton and Jarvis 1946). The ques- 
tion has remained, however, whether these fish were strays from other river 
systems or whether they could be progeny of successful steelhead reproduction 
in the Ventura River (Mark Capelli, Friends of the Ventura River, pers. com- 
mun.). This note briefly describes a useful technique for identifying juvenile 
steelhead and provides data supporting their presence in the Ventura River. 

Rybock, Norton, and Fessler ( 1 975 ) showed that steelhead trout juveniles can 
be distinguished from resident rainbow trout on the basis of otolith nuclei (ON) 
dimensions. Since spawning steelhead trout females are substantially larger than 
spawning resident rainbow trout females and have larger eggs and emergent 
larvae, the earliest formed otolith morphological mark (the ON, or metamorphic 
check) has a larger width and length in steelhead trout than in resident rainbow 
trout. Statistically significant differences between the ON size distributions of 
different samples indicate the existence of distinct fish populations. 

Nine dorsal fin clipped juvenile steelhead trout and 11 wild rainbow trout 
were captured on February 16, 1977 by electroshocking a stretch of the middle 
Ventura River 10.5-12.9 km above the mouth. The marked steelhead trout were 
survivors of a July 1 976 plant of 1 1 ,000 fingerlings. An additional seven unmarked 
rainbow trout were captured in the upper Ventura River (22.6 km above the 



178 



CALIFORNIA FISH AND CAME 



mouth) on February 17, 1977. This location is above Robles Diversion Dam, 
completed in 1959, which prevents upstream migration of fish under most flow 
conditions. 

Otoliths were removed, stored in 100% glycerin, and measured using an 
ocular microscope (see McKern, Norton, and Koski 1974 and Rybock et al. 1975 
for details of the procedure). 

Despite clearing in glycerin, 20% ( 1 1 /54) of the otoliths were unreadable. All 
but two fish, however, had at least one readable otolith. ON measurements 
recorded for the Ventura River trout were within resident and steelhead trout 
ON width and length ranges reported from other Pacific coastal streams 
(McKern et al. 1974, Rybock et al. 1975). Only ON widths were consistently 
distinct enough to accurately measure in all readable otoliths. 

The comparison of ON widths showed distinct distributions for unmarked 
trout taken from above Robles Diversion Dam and marked steelhead trout taken 
from the middle Ventura River (Figures la and 1c). The ON width distribution 
for unmarked trout taken from the middle Ventura River, however, spanned 
nearly the entire range of both marked and unmarked trout (Figure 16). Differ- 
ences in the mean ON widths of the three groups were analyzed by the "t" test 
for small samples (Alder and Roessler 1968). The differences between the 






0) 

E 

3 



5 
4 h 

3 
2 











5 r 
4 

3 
2 
I h 



5 r 

4 

3 
2 
I h 



.225 



n = 7 

w= 0.268 ±0.0224 



(A) 



n = 10 

w= 0.341 ±0.0512 



(B) 




n = 8 

w= 0.390 + 0.0166 



(C) 



J 



258 .290 .322 .354 .386 .419 .451 



Otolith Nuclei ( mm ) 



Figure 1. Frequency distributions and means (±1 S.D. ) of ON widths (millimeters) representing: 
(A) unmarked rainbow trout above Robles Diversion Dam, Ventura River, (B) un- 
marked rainbow trout from below Robles Diversion Dam, and (C) marked steelhead 
rainbow trout from below Robles Diversion Dam. 



NOTES 179 

means were all significant (p<0.05), particularly between the trout collected 
above Robles Diversion Dann and the marked steelhead (p<0.001). 

Unmarked trout captured in the middle Ventura River included fish having 
ON widths within the resident rainbow trout and steelhead trout ranges. The 
former group is either wild resident rainbow trout or planted rainbow trout that 
have moved downstream from the Department of Fish and Game catchable 
trout release sites 25 to 32 km above the mouth. The latter group is either wild 
steelhead trout or hatchery steelhead trout with regenerated dorsal fins. Since 
the marked steelhead were dorsal fin clipped only 8 months prior to the study, 
it is unlikely that they would be misidentified. 

The existence of wild steelhead trout juveniles, as judged by the otolith results, 
implies that some natural spawning and subsequent adult return occurs in the 
river. However, many questions concerning these fish remain: ( i ) what percent- 
age of the adult steelhead entering the Ventura River originate elsewhere, (ii) 
what is the proportion of steelhead trout in the rainbow trout population below 
the diversion dam, (iii) do any steelhead trout pass the diversion dam and 
spawn in the upper river, and ( iv ) what can be done to more effectively protect 
and enhance the natural steelhead trout run? 

ACKNOWLEDGMENTS 
Don Kelley, L. B. Boydstun (California Department of Fish and Game), Mark 
Moore, and Linda Hagen assisted in collecting the fish. Special thanks go to Don 
Kelley who provided the collecting equipment and reviewed the manuscript. 
Mark Moore and Mark Capelli also reviewed the manuscript. 

REFERENCES 

Alder, H L , and E. B. Roessler. 1968. Introduction to probability and statistics. W. M. Freeman and Co., San 

Francisco. 333 p. 
Clanton, D. A., and ). W. jarvis. 1946. Field inspection trip to the Matilija-Ventura watershed in relation to the 

construction of the proposed Malilija Dam (Unpublished report dated May 8, 1946 on file at Fillmore 

Hatchery, Calif. Dep. Fish and Came, Fillmore.) 
McKern, ). L., H. F. Horton, and K. V. Koski. 1974. Development of steelhead trout (Salmo gairdneri) otoliths 

and their use for age analysis and for separating summer from winter races and wild from hatchery stocks. 

Canada, Fish. Res. Bd., lour., 31(81; 1420-1426. 
Rybock, J. T., H. F. Horton, and j. L. Fessler. 1975. Use of otoliths to separate juvenile steelhead trout from 

juvenile rainbow trout. Fishery Bull., 73(3): 654-659 

— William E. Tippets, 2508 Warrego Way, Sacramento, CA 95826. Accepted for 
publication September 1978. 

NOTES ON A HYBRIDIZATION EXPERIMENT 
BETWEEN RAINBOW AND GOLDEN TROUT 

In an earlier note (Gold, Pipkin, and Gall 1976), we presented the results of 
a fortuitous hybridization experiment between a rainbow trout, Salmo gairdneri, 
female and a golden trout Salmo aguabonita male. The hatch and developmental 
data from that cross were limited, but supported field observations that hybridi- 
zation between the two species could occur with ease (Dill 1950; Schreck and 
Behnke 1971; Gold and Gall 1975). This note is a follow-up on that cross. 

By 7 May 1975, only one of the six RT x GT hybrid fingerlings remained alive, 
the rest having succumbed to Chondrococcus columnaris infection or gill dis- 
ease. On 31 December 1976, the survivor, a 2-year-old female, was stripped of 



180 CALIFORNIA FISH AND GAME 

641 normal-sized eggs. These were divided into four lots of roughly 160 eggs 
each and fertilized with the sperm of four 2-year-old males from the domesticat- 
ed rainbow trout strain RTD (Gall 1975). The males were 3 months past their 
spawning peak, but when examined had numerous motile sperm. No golden 
trout males were available for the complementary backcross. The four lots of 
fertilized eggs were water hardened and incubated in separate chambers of a 
Heath-Tecna incubator. Water temperatures during incubation ranged from 
9-1 3 C ( median = 1 1 C ) . At this temperature, RTD eggs normally eye-up within 
13 days and hatch within 29 days (Gall and Pipkin, unpublished data). 

None of the backcross embryos developed normally. After 17 days, roughly 
80% of the eggs showed no indication of embryonic development. The remain- 
der displayed a single, large, dark spot (not a true "eye") accompanied by 
several hemorrhagic streaks. Some of these "spots" grew larger, but by 6 Febru- 
ary none of the embryos had hatched. On 15 February all embryos had ceased 
development and were discarded. A systems failure at the Davis hatchery on 16 
June 1976 resulted in the death of the hybrid female. 

Meristic and morphometric data from the hybrid are compared with mean 
values for rainbow and golden trout from our unpublished data (Table 1). 
Hybrid indices computed after Hubbs and Juronuma (1942) were intermediate 
(.16-.83) for 8 of 27 characteristics. 

Life colors of the hybrid were more or less typical of 5. aguabonita ( Evermann 
1905), although much less pronounced. Parr-type marks, typical of adult 5. 
aguabonita but not adult 5. gairdneri, were not present. The dorsal, caudal, and 
adipose fins were moderately spotted, but the body was almost immaculate 
(Figure 1 ). Approximately 20-25 small spots, crescent-shaped and diffuse as in 
5. gairdneri, were present on the dorsal region of the caudal peduncle, posterior 
to the adipose fin. The parents of the hybrid, S. gairdneri ( 9 ) and 5. aguabonita 
{(S), were heavily and moderately spotted, respectively. The paucity of spots 
on the body of the hybrid was suggestive of the pattern typical of the Paiute 
cutthroat trout (Ryan and Nicola 1976). 

Data indicative of interspecific hybridization among western trouts are abun- 
dant, and have stemmed by-in-large from field studies where one species was 
introduced (by man) into waters occupied by a second species (e.g. Schreck 
and Behnke 1971; Behnke 1972; Gold and Gall 1975). As a result, it has been 
generally assumed that reproductive isolating mechanisms among most western 
trouts are less than complete, and that forced sympatry will usually result in 
introgressive hybridization. The sympatric coastal cutthroat, 5. clarki clarki, and 
anadromous rainbow trout, 5 gairdneri, are among the few cited exceptions 
(Behnke 1972). Miller (1972), however, has pointed out that there is little if any 
experimental data on western trouts regarding mating discrimination or fertility 
of hybrids. 

The failure to obtain backcross progeny from the RT x GT hybrid female may 
reflect a barrier to hybridization between the two species. The experimental 
conditions under which the backcross was made were far superior to those of 
the original parental cross, and there was partial embryogenesis in about 20% 
of the fertilized eggs. It is conceivable that "hybrid breakdown" (Dobzhansky 
1970) was the cause of embryonic mortality, and that reproductive isolating 



Salmo 


S 


almo 


gairdneri 


aguabonita 


(n = 20) 


in 


= 32) 


21.4 




10.4 


59.6 




33.3 


12.3 




12.1 


11.3 




10.7 


14.6 




15.7 


10.1 




9.0 


22.0 




23.9 


18.8 




19.9 


62.5 




60.0 


121.5 




117.3 


135.8 




183.0 



NOTES 181 

TABLE 1. Morphological Data t of RT x CT Hybrid, Salmo gairdneri, and Salmo aguabonita 

Hybrid 
Character (n = 1) 

Standard length, cm 26.9 

Pyloric caecae 43* 

Dorsal fin rays 11 

Anal fin rays 1 1 ' 

Pectoral fin rays 16 

Pelvic fin rays 9 

Branchiostegal rays (total) 22 

Gill rakers (left) 18 

Vertebrae 62* 

Scales, lateral line 1 23 

Scales, lateral series 1 54* 

Scales above lateral line 30 

Scales below lateral line 31 

Interneural bones 1 3 

Interhaemal bones 1 3 

Thousands of standard length 

Body depth 264* 

Head length 233 

Head width 145 

Least interorbit 70 

Occiput to snout length 167 

Maxilla length 93* 

Caudal peduncle length 146 

Caudal peduncle depth 1 1 3 

Predorsal length 470 

Preanal length 751 

Prepectoral length 265 

Prepelvic length 544 

Dorsal, base length 141 

Anal, base length 116 

Pectoral length 163* 

Pelvic length 1 38* 

Eye diameter 43 

• Values intermediate tjetween means of parental species (cf texti 

\ Data for S. gairdneri m\A S. aguabonitu represent sample means fX). 

mechanisms among western trouts are more complete than presently believed. 
Busack (1977), for example, has recently presented evidence of two closely 
related inland cutthroat trout forms which coexist sympatrically without appar- 
ent gene exchange. The introgression frequently observed among western trouts 
in nature may indicate the well-known relationship between hybridization and 
habitat disruption (Anderson 1949). 



268 


248 


235 


289 


126 


134 


75 


74 


177 


209 


87 


125 


164 


148 


104 


101 


509 


536 


782 


773 


219 


252 


558 


560 


139 


140 


91 


101 


127 


181 


103 


145 


45 


71 



182 



CALIFORNIA FISH AND CAME 




Figure 1. Lateral view of female Salmo gairdneri -x. Salmo aguabonita hybrid. 



ACKNOWLEDGMENTS 

We thank S. J. Nicola for reading an early draft of this note. The study was 
supported by Federal Aid in Fish Restoration funds as California project D-J 
F-28-R, Trout Genetics. 

REFERENCES 

Anderson, E. A. Introgressive hybridization. )ohn Wiley and Sons, Inc., New York, 109p. 

Behnke, R. ). 1972. The systematics of salmonid fishes of recently glaciated lakes. Canada, Fish. Res. Bd., )., 29: 

639-671. 
Busack, C. A. 1977. Genetic variation among populations of Paiule trout iSalmo clarkl seleniris) . Qf^- Univ. of 

Calif.; 1977. 155p. M.S. Thesis. 
Dill, W. A. 1950. A report on the golden trout fishery of California. Calif. Dept. Fish and Game, Inland Fish. 

Admin. Rep., 50-44. 28p. (mimeo). 
Dobzhansky, T. 1970. Genetics of the evolutionary process. Columbia Univ. Press, New York and London. 

505p 
Evermann, B. W. 1905. The golden trout of the southern High Sierras. U. S. Bur Fish. Bull., 25: 1-51. 
Call, G. A. E. 1975. Genetics of reproduction in domesticated rainbow trout. ). Anim. Sci., 40: 19-28. 
Gold, ). R, and C. A. E. Gall. 1975. The taxonomic structure of six golden trout (Salmo aguabonita) populations 

from the Sierra Nevada, California. Calif. Acad. Sci., Proc, XL(IO): 243-263. 
Cold, ). R., R. E. Pipkin, and G. A. E. Call. 1976. Artificial hybridization between rainbow (Salmo galrdneri) and 

golden trout (Salmo aguabonita) . Copeia, 1976(3): 597-598. 
Hubbs, C. L., and K. Kuronuma. 1942. Analysis of hybridization in nature between two species of Japanese 

flounders. Papers Michigan Acad. Sci., Arts, Letters, 27: 267-306. 
Miller, R. R. 1972. Classification of the native trouts of Arizona, with the description of a new species, Salmo 

apache. Copeia, 1972(3); 401^22. 



NOTES 183 

Ryan,). H., andS. ). Nicola. 1976. Statusof the Paiute cutthroat trout, S^/mo c/arki se/eniris Snyder, in California. 
Calif. Dept. Fish and Game, Inland Fisheries Admin. Rep., 76-3 (mimeo). 

Schreck, C. B., and R. ). Behnke. 1971. Trouts of the upper Kern River basin, California, with references to 
systematics and evolution of western North American Salmo. Canada, Fish. Res. Bd. ]., 28: 987-998. 

— / R- Gold, R. E. Pipkin, and G. A. E. Gall, Fisheries Biology Research Facility, 
Department of Animal Science, University of California, Davis, California 
95616. Dr. Gold's present address: Genetics Section, Texas A&ivl University, 
College Station, Texas 77843. Accepted for publication November 1978. 



CALIFORNIA CONDOR SURVEY, 1978 

A cooperative survey of California Condors, Gymnogyps californianus, was 
conducted 17 and 18 October 1978. Fifty observation stations were staffed by 
110 observers from noon until condor flight activity ceased each day, usually 
about 5:00 p.m. All condor observations were recorded by time of day, direction 
of travel, age of birds (adult, immature, or undetermined), and distinguishing 
characteristics of individual birds (e.g., missing flight feathers). Total sightings 
were later evaluated to arrive at a probable minimum number of condors seen. 
Evaluation procedures remained the same as in previous surveys (see Mallette 
and Borneman, California Fish and Game 52(3) :1 85-203, 1966). Records were 
also kept of other raptorial birds seen during the survey. 

Most stations reported high broken cirrus clouds on 1 7 October but thick haze 
reduced visibility at most lowland stations. Temperatures at higher elevations 
were 1 5.5 C to 21 .0 C; lower stations reported 21 C to 30 C. Winds were mostly 
from the southwest at less than 16 kmph. FHowever, some higher elevations 
reported winds of 32 to 48 kmph. 

On 1 8 October, winds shifted to the southeast and decreased somewhat. FHigh 
clouds increased, and temperatures rose slightly at all stations. 

Thirty-six total condor sightings were reported by 11 stations on 17 October; 
these represented a minimum of 12 individual condors (7 adults, 3 immatures, 
2 unclassified). On 18 October, 15 stations reported 50 sightings; analysis in- 
dicated these represented at least 13 condors (7 adults, 4 immatures, 2 unclassi- 
fied). 

We do not know what proportion of the total population was accounted for 
on this survey, but other data collected in 1978 indicate that less than one-half 
of the condors were seen. Apparently some birds remained outside the survey 
area during the 2-day period. One encouraging note is that at least four immature 
( under 5 years of age ) condors were seen, about as many as our nesting surveys 
have accounted for since 1974. This indicates excellent survival during the first 
few years of life and also suggests that our recent estimates of condor production 
may have been somewhat low. 

Eleven other raptor species were observed (Table 1 ). 

This report was prepared with the approval of the California Condor Recovery 
Team and is a contribution from Endangered Wildlife Program, E-W-3, California 
Department of Fish and Came, Nongame Wildlife Investigations. 



184 CALIFORNIA FISH AND GAME 

Table 1. Raptors Observed During the Condor Survey, 17 and 18 October 1978 

Numbers 
Species 17 Oct. 18 Oct. 

Turkey Vulture (Cathartes aura) 203 368 

Golden Eagle {Aquila chrysaetos) 82 73 

Sharp-shinned Hawk (Accipiter slriatus) 20 18 

Cooper's Hawk (A. cooperii] 26 16 

Red-tailed Hawk [Buteo jamaicensis) 200 173 

Swainson's Hawk [B. swainsoni) 2 38 

Ferruginous Hawk (B. regalis) 6 3 

American Kestrel i Faico sparverius) 53 51 

Prairie Falcon (F. mexicanus) 5 2 

Peregrine Falcon (F. peregrinus) 1 — 

Marsh Hawk (Circus cyaneus) 4 6 

Unidentified raptors 42 _37 

644 785 

— San ford R. Wilbur, U. S. Fish and Wildlife Service, 1190 E. O/ai Ave., Ojai, 
California 93023; Robert D. Mallette, California Department of Fish and Game, 
1416 Ninth St., Sacramento, California 95814; and John C Borneman, National 
Audubon Society, 2208 Sunridge Drive, Ventura, California 93003. Accepted 
for publication February 1979. 

THE RELATIONSHIP BETWEEN MEGALOPAE OF THE 

DUNGENESS CRAB, CANCER MAGISTER, AND THE 

HYDROID, VELELLA VELELLA, AND ITS INFLUENCE 

ON ABUNDANCE ESTIMATES OF 

C MAGISTER MEGALOPAE 

INTRODUCTION 

Crab fishermen have long noted crab megalopae hanging onto floating objects 
and crab trap lines. Weymouth (1918) noted the presence of Dungeness crab, 
Cancer magister, megalopae on bells of several pelagic jellyfishes. The tendency 
of crab megalopae to attach to floating objects could make them unavailable to 
abundance surveys conducted with plankton nets sampling the open water 
column. In May 1975, I noted C /r7a^/5^er megalopae among the tentacles of the 
neustonic hydroid Velella velella. This hydroid occurred in high densities in the 
spring of 1975 while this year class of C mj^/s^e/' megalopae were making their 
inshore movement to crab nursery areas (Lough 1976). I investigated the degree 
of association between these two organisms to see whether a significant propor- 
tion of megalopae was removed from the water column. 

MATERIALS AND METHODS 
V. velella were sampled individually with dip net on 9 May 1975 from the 
Bodega Marine Laboratory's research boat. Stations were made along a transect 
from Bodega Bay, California, to 24 km offshore in a southwest direction. These 
stations were opportunistically determined due to the patchy distribution of V. 
velella. The individual hydroids were examined and associated crab megalopae 
were removed and counted. The gut contents of five megalopae obtained from 



NOTES 185 

I/, velella were examined for hydroid tissue. V. velella washed ashore were 
sampled and checked for the presence of crab megalopae. 

A similar cruise was taken along the same transect in May 1976. 

RESULTS 
Samples obtained from stations between 0.8 km and 10.0 km from shore 
showed the presence of C. magister megalopae on 16-88% of the hydroids 
(Table 1 ). No megalopae were found on V. velella which were either beached 
or beyond 10.0 km. 

Table 1. Sampling Data and Degree of Association of Velella velella and Cancer magister 
Megalopae 

Distance from No. V. velella No. with Percent V. velella 
Station shore (km) sampled crab larvae with crab larvae 

1 onshore 200 0.0 

2 0.8 35 13 37.1 

3 1.6 32 22 68.8 

4 4,8 25 22 88 

5 8.0 10 5 50.0 

6 9.6 25 4 16.0 

7 11.2-24.0 100 0' 0.0 

In 59 of the observed crustacean-hydrozoan associations, only 1 C. magister 
megalopa was present per individual hydroid. In six instances two were ob- 
served and, in one case, three were present on a single V. velella. In all cases, 
the megalopae were among the gonozooids underneath the hydroid float. Ap- 
parently no megalopae were harmed by the hydrozoan nematocysts; all were 
active and in good condition. 

Other animals present on the hydrozoan were megalopae of another Cancer 
species, adult barnacles of a Zep^5 species, and barnacle cyprid larvae. Animals 
found inside the gonozooids were apparent food items and consisted of zoeae 
of the crab Pugettia producta, barnacle cyprids, and a cumacean. 

The guts of the five megalopae were filled with tissue containing large numbers 
of unreleased V. velella nematocysts. One megalopa was preserved in the act 
of eating an entire gonozooid with its attached medusae buds. 

During the dip net sampling in May 1975, few free swimming megalopae were 
observed. Personnel from the California Department of Fish and Came also 
observed C. magister megalopae on V. velella outside San Francisco Bay but 
found that megalopae were not present in plankton net samples taken when V. 
velella was present (Tasto et al. 1977). 

No V. velella were found during the May 1976 cruise, nor were any observed 
in coastal waters or on the beach in the Bodega Bay area that year; however 
C. m.s^/^/e/' megalopae were abundant and could be seen swimming near the 
surface. I was able to observe these larvae as two distinct bands, one about 2-km 
wide from 1 km offshore and another approximately 5-km wide from 8 km 
offshore. A visual estimate of the average abundance indicated a density of 
roughly 1 /m^. 

DISCUSSION 

V. velella appears to provide several benefits to megalopae of C. magister. It 
provides (i) an abundant source of food, (ii) shelter from predatory pelagic 



186 CALIFORNIA FISH AND GAME 

fishes such as salmon which feed on them (Anon. 1949), and (iii) possible 
transportation into nearshore juvenile crab habitats. It is not known whether the 
presence of V. velella makes a significant contribution to year class abundance 
of Dungeness crabs. These hydroids only occur sporadically along the central 
California coast and their presence is unpredictable from year to year. 

Ccincer nicigister vr[C^A\o\iA^ were not present in the surface waters or in net 
samples when V. velella was abundant, even though the crabs were abundant 
on the hydroids. Most surveys conducted to assess crab larval abundance rely 
on sampling with plankton nets (Sandifer 1973; Lough 1976; Tasto et al. 1977). 
Several million V. velella were present in the coastal waters near Bodega Bay 
in 1975 so the total number of crab megalopae associated with this hydroid 
could have been very high. The presence of V. velella, therefore, must be 
accounted for in any attempt to estimate Cancer ma^/s/ermegalopal abundance. 

ACKNOWLEDGMENTS 
I would like to thank Cadet Hand and Jerry Tinkess of the Bodega Marine 
Laboratory for graciously allowing me the use of the facilities. This work is a 
result of research sponsored by NOAA, Office of Sea Grant, Department of 
Commerce, under grant #04-6-158-44110. The U.S. Government is authorized 
to produce and distribute reprints for governmental purposes notwithstanding 
any copyright notation that may appear hereon. 

REFERENCES 

Anonymous 1949. Crab larvae as food for the silver salmon at sea. Fish Comm Oregon Res. Briefs 2: 17. 
Lough, C. 1976. Larval dynamics of the Dungeness crab, Cancer magisler, off the central Oregon coast, 

1970-71. U.S. Fish Wildl. Serv , Fish Bull. 74: 353-376. 
Sandifer, P. 1973 Distribution and abundance of decapod crustacean larvae in the York River estuary and 

adjacent lower Chesapeake Bay, Virginia, 1968-1969. Ches. Sci, 14: 235-257. 
Tasto, R. N., P N Reilly, D D Mogelberg, and S. E Hatfield. 1977. Crab critical stage project studies. Pages 

10-29 in H. C. Orcutt, compiler. Dungeness crab research program, report for the year 1977. Calif. Dept. Fish 

Came, Mar. Resour. Admin Rep. 77-22. 
Weymouth, F. 1918. Contributions to the life history of the Pacific edible crab. Canada, B.C. Comm. Fish, Rep. 

for 1917 (3): 81-90. 

— Daniel E. Wickham, University of California, Bodega Marine Laboratory, 
Bodega Bay, California 94923. Accepted for publication February 1979. 

WINTE-R FOOD HABITS OF FISHERS, MARTES PENNANTI, 
IN NORTHWESTERN CALIFORNIA 

Very little is known about food habits of California fishers. Most information 
on this uncommon mustelid is summarized by Grinnell, Dixon, and Linsdale 
(1937). Recently a study of fisher abundance and distribution in California was 
completed by Schempf and White (1977). Currently, Humboldt State Univer- 
sity, the U.S. Forest Service, and the California Department of Fish and Game 
are cooperating in a study of fishers in a study area in Trinity National Forest, 
Trinity County. 

Chief foods of fishers in the Pacific coastal states are porcupines, squirrels, 
woodrats, mice, marmots, mountain beavers, quail, and grouse (Ingles 1965). 
A study conducted in Ontario, Canada, revealed that porcupines, muskrats, and 
snowshoe hares dominated the winter diet; a variety of other prey, such as 
squirrels, voles, mice, shrews, grouse, and jays was also consumed ( Clem 1 975 ) . 



NOTES 1 87 

Mice, squirrels, shrews, birds, fruit, and carrion were items most commonly 
found in fisher stomachs in a New Hampshire study (Kelly 1977). 

From December 1977 through February 1978, eight fisher carcasses obtained 
from the Trinity County study area were made available for food habits study. 
Admittedly, the sample size is small, but fishers have been protected in California 
since 1946 and opportunities to investigate their food habits are extremely 
limited. 

The vegetation of the study area consists of a mosaic of plant communities 
including Klamath montane forest with Douglas-fir, Klamath montane forest with 
yellow pine, Coast Range montane forest, Oregon oak forest; mixed evergreen 
forest with chinquapin, and mixed evergreen forest with rhododendron (Kuch- 
ler 1977). Elevations range between 610 and 1,070 m. 

METHODS AND MATERIALS 

Stomach contents were removed from fisher carcasses and preserved in 10% 
formalin. Identification was made by the Food Habits Section of the California 
Department of Fish and Game's Wildlife Investigations Laboratory at Sacra- 
mento. 

All food material was washed and screened in a sieve measuring 14 squares 
per cm. Examination was done with a dissecting microscope and all identifiable 
items were grouped by categories. Hair was examined with a compound micro- 
scope. Plant and insect fragments and mammalian teeth and hair were identified 
by comparing them with known reference materials and by referring to appropri- 
ate texts. 

Items were tallied by frequency of occurrence. Volumes were visually estimat- 
ed in increments of 5%; volumes estimated to be less than 5% were recorded 
as a trace. 

RESULTS AND DISCUSSION 

The most significant food item, both by frequency of occurrence and by 
volume, was false truffle (subterranean fungi) (Table 1 ). False truffles have not 
been recorded in previous fisher studies; in our study, spores and tissue occurred 
in four samples. Three of these samples also contained hair from western harvest 
mice, deer mice, and black-tailed deer. False truffle is eaten by squirrels and 
other rodents in the southern United States (Miller and Halls 1969) and western 
gray squirrels in California have similar food habits (Stienecker and Browning 
1970; Steinecker 1977). Whether fishers selectively feed on fungi or acquire 
them indirectly from their prey has not been resolved. However, one sample 
contained 90% false truffle by volume, compared with 10% western harvest 
mouse hair. None of the samples contained squirrel hair and fungi together. 
Selection of fungi by fishers is, therefore, a possibility. 

The second most important food item by volume was bovine; however, this 
food item occurred in only one of eight samples (12.5%) and was probably 
carrion. Fishers were found to feed on carrion in the White Mountains of New 
Hampshire (Kelly 1977). 

Deer hair was identified in two stomachs. The occurrence of deer in fisher 
digestive tracts has also been reported by other researchers. Frequency of occur- 
rence of deer was 2.8% in fishers studied in Ontario, Canada (Clem 1975). In 
the New Hampshire study, deer hair found in fisher stomachs was attributed to 
carrion or trap-bait (Kelly 1977). 



188 CALIFORNIA FISH AND GAME 

TABLE 1. Stomach Contents of Eight Fishers Collected During the 1977-78 Winter Season 
in Trinity County, California 

Frequency Volume 
Food item (%l (%) 

Plant 

False truffle (Ifh/zopogonsp), (spores and tissues) 50.0 28.0 

-Bark 50.0 7.5 

Douglas-fir { Pseudotsuga msnziesii) , (leaves) 50.0 0.6 

White fir (Abies concolor), (leaves) 12.5 0.6 

Ceanothus iCeanothus sp), (leaves) 12.5 T 

Oak [Quercus sp), (leaves) .■ 12.5 T 

Forb (Dicotyledneae), (leaves) 12.5 T 

Grass (Cramineae), (leaves and stems) 12.5 T 

Moss { Selaginella sp) , (leaves and stems) 12.5 T 

Animal 

Fisher (Martes pennanti) , (hair) 62.5* 0.6 

Black-tailed deer (Odocoileus hemionus) , (hair) 25.0 8.8 

Deer mouse (/'eramyscw sp), (hair) 25.0 3.1 

Beetle (Coleoptera), (larvae, exoskeleton) 25.0 T 

Bovine (Bostaurus), (hair, flesh) 12.5 11.3 

Brush rabbit (Sylvilagus bachmanh 12.5 10.0 

Broad-handed mole (Scapanus latimanus) , (hair) 12.5 8.1 

Western gray squirrel (Sciurus gnseus) , (hair and teeth) 12.5 7.5 

Wesierr^ har\/es\ mouse { Peithrodontomys megalotus) , (hair) 12.5 1.3 

Mammal claws 12.5 0.7 

Arthropoda (fragments) 12.5 T 

Miscellaneous 

Grit 62.5 8.1 

Bone fragments 12.5 2.5 

Flesh, unidentified 12.5 1-3 

100.0 

T = Trace 

• Usually ingested while grooming. 

No porcupine remains were found in our specimens, but evidence of porcu- 
pine-fisher interaction in the study area has been reported; 1 of 10 live-captured 
fishers and 2 necropsied fishers had quills embedded in their hides (C. Mullis, 
student, Humboldt State University, pers. commun.). Similarly, porcupine was 
not found in 40 fisher stomachs examined in New Hampshire, but 15% of 89 
fishers contained quills in their pelts (Kelly 1977). 

ACKNOWLEDGMENTS 
Tim Burton, California Department of Fish and Game Wildlife Biologist, and 
Curt Mullis, a student at Humboldt State University, provided the specimens for 
examination. Oscar Brunetti, California Department of Fish and Game, Wildlife 
Pathologist, confirmed the identification of false truffle. 

REFERENCES 

Clem, M. K. 1975. Interspecific relationship of fishers and martens in Ontario during winter Pages 165-182 ir 
R. Phillips and C. Jonkel, eds. Proceedings of the 1975 predator symposium. Montana For. and Conserv. Exp 
Sta., Missoula, MT. 

Crinnell, )., j. S. Dixon, and). M Linsdale. 1937. Furbearing mammals of California. Univ Calif Press, Berkeley 
CA, 2 vols. 

Ingles, L. C. 1965. Mammals of the Pacific states Stanford Univ. Press, Stanford, CA. 506 pp. 



NOTES 1 89 

Kelly, C. M. 1977. Fisher biology in the White Mountain National Forest and adjacent area. Ph.D. Dissertation. 

Univ. of Mass. Amherst, MA. 
Kuchler, A. W. 1977. The map of the natural vegetation of California. Dep. of Ceogr. Univ. of Kansas, Lawrence, 

KS. 
Miller, H. A., and L. K. Halls. 1969. Fleshy fungi commonly eaten by southern wildlife. Southern For. Exp. Sta., 

New Orleans, LA. 28 pp. 
Schempf, P. F., and M. White. 1977. Status of six furbearer populations in the mountains of northern California. 

U.S. Dep. of Agri., For. Serv., Calif. Region. 51 pp. 
Stienecker, W., and B. Browning. 1970. Food habits of the western gray squirrel. Calif. Fish Came 56(1 ): 36-48. 
Stienecker, W. 1 977. Supplemental data on the food habits of the western gray squirrel. Calif. Fish Game 63 ( 1 ) : 

11-21. 

— William E. Crenfell, California Department of Fish and Came, 987 Jedsmith 
Drive, Sacramento, CA 95819, and Maurice Fasenfest, 1542 Maple Street, San 
Mateo, CA 94402. Accepted for publication September 1978. 

AN ANTI-ROLL BEACH SEINE 

The netting of a beach seine will often roll up into a tight "rope" when used 
where submerged, attached plants, such as eelgrass, Zostera marina, are present. 
When this occurs, fishes can no longer be caught in the seine. 

My observations indicate that net rolling is caused by attached plant leaves 
being "caught" by the netting of the seine. The attached leaves "escape" the 
seine by dragging the netting down, in front of, below, and behind the foot rope 
as the seine passes through and over attached vegetation. This causes the netting 
to become rolled up into a tight "rope". 

An anti-roll beach seine was constructed for use in eelgrass areas. It was made 
of a rectangular piece of 10-mm stretched mesh cotton netting suspended 
between two wooden poles (Figure 1). The head rope was buoyed by two 
120-mm long and 80-mm wide foam floats. The main foot rope was weighted 
to 1 .1 kg with 7-mm wide pencil lead that was bent and coiled around the main 
foot rope. A secondary foot rope was attached to the netting in several places 
as well as to the ends (Figure 1). It was weighted to 1.25 kg in the manner 
described for the main foot rope. Four chains were tied with nylon twine to both 
foot ropes (Figure 1). Each chain weighed 0.3 kg and was constructed of 
nineteen 42-mm long and 4.8-mm thick links. 

This seine did not roll because the forward and downward drag of the eelgrass 
leaves against the netting was counteracted by a backward drag of the second- 
ary foot rope and chains against the middle of the seine. This anti-roll beach 
seine can be used to capture fishes wherever submerged vegetation causes other 
beach seines to roll. 

ACKNOWLEDGMENTS 
R. Wisner, Jr. and F. Button were helpful in the development of this seine. 

Constructive criticism for the manuscript was provided by J. A. Wiens and R. 

Olson. This is contribution number 67 of the Behavioral Ecology Laboratory, 

Oregon State University. 

— Range D. Bayer, Department of Zoology, Oregon State University Marine 
Science Center, Newport, Oregon 97365. Present address: 423 S. W. 9th, New- 
port, Oregon 97365. Accepted for publication December 1978. 



190 



CALIFORNIA FISH AND CAME 




Figure 1. Back view of the anti-roll beach seine. 



NOTES 



191 



TERM FETUSES FROM A LARGE COMMON THRESHER 
SHARK, ALOPIAS VULPINUS 

Little is known of the life history of the common thresher shark. It has been 
determined that this ovoviviparous species attains maturity at a length of approx- 
imately 4.2 m, and, on a worldwide basis, probably reaches a maximum length 
of some 6 m (Bigelow and Schroeder 1948). Most threshers taken in California 
waters are less than 2.4 m in length (Roedel and Ripley 1950; Fitch 1974), 
although larger specimens are often captured off southern California, particularly 
by anchovy purse seiners and barracuda gill-netters during summer months (J. 
Fitch and D. Schultze, Calif. Dept. Fish and Game, pers. commun.). Unfortu- 
nately, few of these large threshers have been closely examined before being 
cleaned. This note describes term fetuses taken from one such specimen. 

On 3 June 1977, Michael McCorkle of the commercial fishing vessel PIE FACE 
landed a large female thresher that had become entangled in his gill nets the 
previous night. The nets had been set in 13 fm of water approximately 2 nautical 
miles off Solimar Beach near Ventura, California. The length of the fish was 
estimated at greater than 4.6 m and its weight was measured at 295 kg. When 
the thresher was cleaned, four large fetuses were removed, two of which were 
badly mutilated in the process. The intact specimens were donated to the 
University of California at Santa Barbara, and subsequently deposited at the 
Museum of Ichthyology in the Department of Biological Sciences. 




Figure 1. Male and female term fetuses of the common thresher shark. Photograph by G. M. 
Wellington, June 1977. 



The two fetuses had been very near birth, as evidenced by their lack of 
umbilical scars and their large size (Figure 1 ). The male was 1417 mm in total 



192 CALIFORNIA FISH AND CAME 

length and weighed 8.8 kg fresh, while the fennale was 1386 mm long and 
weighed 7 .1 kg. These specimens approach the maximum fetal size of 1550 mm 
reported by Bigelow and Schroeder (1948). Moreover, free-living threshers 
considerably smaller than the fetuses have been taken off California ( Herald and 
Ripley 1951 ), as well as off the eastern United States (Bigelow and Schroeder 
1948). 

In 1954, another large thresher carrying four term fetuses was captured off 
Newport Beach (Joseph 1954). Although it was larger than the one reported 
here (approximately 5.4 m) the fetuses were somewhat smaller and still exhibit- 
ed umbilical scars. 

As a final note, the litter size of the common thresher shark is invariably 
reported as ranging from two to four pups ( Bigelow and Schroeder 1 948; Roedel 
and Ripley 1950). However, McCorkle (pers. commun.) once captured a 
thresher that carried six fetuses. 

ACKNOWLEDGMENTS 
In addition to Michael McCorkle, I wish to thank my colleagues at the U. C. 
Santa Barbara Marine Science Institute, especially Floyd DeWitt, who obtained 
the specimens, and Jerry Wellington, who photographed them. John Fitch and 
Don Schultze, California Department of Fish and Game, kindly provided useful 
commercial catch data. 

REFERENCES 

Bigelow, H. B., and W. C. Schroeder. 1948. Sharks. Pages 59-546 in Fishes of the western North Atlantic. Part 
1. Sears Found. Mar. Res., Mem. (1). 

Fitch, J. E. 1974. Offshore fishes of California. 5th ed. Calif. Dept. Fish Came, Sacramento. 80 pp. 

Herald, E. S., and W. E. Ripley. 1951. The relative abundance of sharks and bat stingrays in San Francisco Bay. 

Calif. Fish Came 37: 315-329. 
Joseph, D. C. 1954. A record-size thresher from southern California. Calif. Fish Came 40: 433^35. 
Roedel, P. M., and W. E. Ripley. 1950. California sharks and rays. Calif. Dept. Fish Game, Fish Bull. (75). 88 

PP 

— Mark A. Hlxon, Department of Biological Sciences and Marine Science Insti- 
tute, University of California, Santa Barbara 93 1 06. Accepted for publication 
February 1979. 



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